LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 

GIFT  OF 


BIOLOGY 

LIBRARY 

G 


HUMAN    PHYSIOLOGY 

PERSONAL  HYGIENE  AND  PUBLIC  HEALTH 


I 


From  an  X-ray  Photograph  of  the  Hand,  showing  a  Bullet 
imbedded  in  the  Flesh. 


PRACTICAL   LESSONS 


IN 


HUMAN    PHYSIOLOGY 

PERSONAL  HYGIENE  AND 
PUBLIC    HEALTH 


FOR    SCHOOLS 


BY 


JOHN    I.    JEGI,    M.S. 

PROFESSOR   OF   PHYSIOLOGY*  AND    PSYCHOLOGY,    STATE   NORMAL 

SCHOOL,    MILWAUKEE 
AUTHOR   OF    "  SYLLABUS    OF    HUMAN    PHYSIOLOGY  " 


FULL  Y  ILL  USTRA  TED 


gorfc 
THE   MACMILLAN    COMPANY 

LONDON:   MACMILLAN  &  CO.,  LTD. 
1903 

All  rights  reserved 


BIOLOGY 

LIBRARY 

G 


COPYRIGHT,  1903, 
BY  THE  MACMILLAN  COMPANY. 


Set  up,  electrotyped,  and  published  August,  1903. 

» 


J.  S.  Cashing  &  Co.  -  Berwick.  &  Smith  Co. 
Norwood,  Mass.,  U.S.A. 


PLAN   OF   THE    BOOK 

THERE  are  so  many  good  text-books  published  to-day 
on  all  school  subjects  that  whenever  a  new  one  comes 
from  the  press  all  persons  interested  examine  it  eagerly 
to  see  what  new  features  it  may  contain.  The  reasons 
why  this  text  was  written  are  given  in  brief  in  the 
following  paragraphs. 

Sequence  of  Topics.  —  In  any  science  the  order  in 
which  the  various  subjects  are  brought  to  the  learner's 
mind  is  a  matter  of  the  utmost  consequence.  Unless 
the  various  topics  are  presented  in  a  logical  or  natural 
order,  the  pupils  fail  to  grasp  the  connection  between 
them.  In  texts  where  each  chapter  is  complete  in 
itself,  and  need  have  little  relation  with  what  has  pre- 
ceded or  with  what  follows,  the  pupils  may  learn  much 
that  is  valuable  and  useful,  but  this  knowledge  must 
always  remain  scrappy,  disconnected,  and  unorganized. 

The  logical  arrangement  of  subject-matter  has  long 
been  regarded  as  an  essential  feature  of  a  good  text- 
book. In  this  book  an  attempt  is  made  to  present  the 
subject  in  such  a  way  that  the  pupil  shall  see  the  rela- 
tion which  the  various  tcpics  sustain  to  each  other  and 
to  the  entire  body  of  knowledge.  In  other  words,  the 

V 

144855 


vi  PLAN   OF  THE   BOOK 

" story  plan"  has  been  adopted  so  far  as  it  is  possible 
in  the  treatment  of  physiology. 

The  cell  is  taught  as  the  unit  of  structure  and  func 
tion  from  the  very  first.  The  pupil  learns  something 
of  the  life  history  of  the  amoeba  in  the  first  chapter. 
He  studies  the  medium  in  which  the  amoeba  lives,  and 
learns  how  the  amoeba  gets  its  food,  and  how  it  elimi- 
nates its  waste  products.  Then  he  learns  that  each  cell 
of  the  human  body  is  a  living,  acting  unit  that  resem- 
bles the  amoeba  in  its  life  history.  Then  follows  a 
study  of  the  medium  in  which  the  cells  of  the  human 
body  live,  and  from  which  they  obtain  their  food,  and 
to  which  they  give  off  their  wastes.  This  naturally 
leads  to  a  consideration  of  the  whole  subject  of  food  — 
solids,  liquids,  and  gases. 

After  learning  what  the  different  foods  are,  where  they 
come  from,  and  the  amount  required,  he  must  see  how 
each  gets  into  the  blood  and  becomes  part  of  the  blood. 
In  the  chapter  on  Respiration  he  learns  how  oxygen  — 
the  simplest  food  —  gets  into  the  blood.  Then  follows 
a  chapter  on  Digestion  and  one  on  Absorption,  to  see 
how  the  solid  and  liquid  foods  are  prepared  for  the 
blood  and  how  they  enter  the  blood.  After  the  three 
kinds  of  food  have  been  traced  into  the  blood  he  studies 
Circulation,  to  learn  how  the  foods  are  carried  to  the 
various  cells  in  all  parts  of  the  body.  Next  he  learns 
what  becomes  of  the  foods  in  the  cells,  what  uses  they 
serve,  and  what  waste  products  they  form.  Then  these 
waste  materials  are  traced  to  the  organs  of  excretion, 
and  he  learns  how  they  are  taken  out  of  the  blood  and 


PLAN   OF  THE   BOOK  vii 

how  they  are  eliminated  from  the  body.  This  com- 
pletes the  story  of  the  foods,  which  is  told  in  the  first 
twelve  chapters. 

Bones  and  muscles  are  next  discussed,  to  learn  how 
some  of  the  energy  of  the  foods  is  used  in  moving  any 
part  of  the  body  and  in  locomotion.  These  two  topics 
must  be  studied  together  so  as  to  bring  out  the  fact 
that  the  bones  serve  as  levers  for  the  muscles,  and 
hence  such  activities  as  standing,  walking,  running, 
swimming,  breathing,  talking,  etc.,  are  made  possible. 

Next  follows  a  study  of  the  nervous  system  and  the 
special  senses,  to  see  how  all  the  processes  and  activities 
of  the  human  body  are  controlled  and  unified.  This 
furnishes  an  opportunity  to  review  all  the  other  systems 
and  at  the  same  time  to  study  them  in  a  new  light.  The 
last  three  chapters  treat  bacteria  and  diseases,  general 
sanitation,  and  accidents  and  emergencies  respectively. 

Hygiene.  —  The  central  thought  of  the  entire  book  is 
personal  hygiene  and  public  health.  Such  facts  of 
structure  are  taught  as  are  necessary  to  enable  the 
pupil  to  understand  the  laws  of  health.  Hygiene  will 
be  dogmatic  and  uninteresting  if  one  does  not  know 
how  an  organ  or  a  system  works,  and  a  knowledge  of 
function  demands  a  certain  amount  of  anatomy.  It  is  a 
mistake  to  attempt  to  teach  hygiene  without  the  neces- 
sary background  of  physiology  and  anatomy.  For  that 
reason  the  subject  of  hygiene  is  considered  in  connec- 
tion with  each  topic  discussed  and  generally  in  the 
same  chapter,  but  there  are  several  chapters  devoted 
wholly  to  hygiene. 


viii  PLAN  OF  THE   BOOK 

The  subject  of  bacteria  and  transmissible  diseases  is 
treated  in  a  simple  way  so  as  to  bring  it  within  the 
comprehension  of  the  pupils.  While  this  subject  is 
not  generally  discussed  in  elementary  physiologies,  it 
cannot  be  denied  that  it  forms  an  important  phase  of 
personal  hygiene  and  public  health.  The  schools  can 
do  much  to  make  people  more  intelligent  on  this  im- 
portant question  if  they  will  teach  such  simple  facts  as 
are  presented  in  these  two  chapters. 

The  Alcohol  Question.  —  The  subject  of  alcohol  is 
treated  in  the  chapter  on  Drinks  and  Narcotics  in  the 
early  part  of  the  book.  Then  in  connection  with  the 
discussion  of  each  system  throughout  the  book,  there 
is  a  brief  statement  of  the  specific  effect  of  alcohol 
upon  that  system.  An  attempt  has  been  made  to  state 
the  truth  so  far  as  it  is  known  at  the  present  time  and 
without  coloring  the  facts.  No  good  can  come  from 
the  extravagant  statements  so  often  made  by  well-mean- 
ing persons  in  discussing  this  subject  in  books  and 
magazines  for  the  young. 

The  treatment  of  stimulants  and  narcotics  is  ample 
enough  to  meet  the  requirements  of  the  laws  of  those 
states  which  prescribe  instruction  on  the  effects  of 
stimulants  and  narcotics  on  the  human  system,  and,  at 
the  same  time,  it  is  scientific,  being  based  on  the  latest 
researches. 

Exercises  and  Experiments.  —  This  text-book  is  not 
made  on  the  laboratory  plan,  and  yet  a  large  number 
of  simple  exercises  and  experiments  that  can  be  per- 
formed with  inexpensive  apparatus  are  suggested  in 


PLAN  OF  THE   BOOK  ix 

the  body  of  the  text.  Instead  of  placing  the  exercises 
in  a  separate  chapter  at  the  end  of  the  book,  they 
occur  in  connection  with  the  sections  which  they  are 
intended  to  illustrate.  In  this  way  the  exercises  be- 
come part  of  the  regular  lessons,  and  the  pupil  learns 
to  associate  them  with  the  proper  facts. 

While  most  of  these  exercises  are  so  simple  that 
they  can  be  shown  with  such  appliances  as  are  found 
in  the  ordinary  kitchen,  they  should  be  regarded  as  an 
essential  part  of  the  text.  The  experiments  should  be 
performed  by  the  teacher  before  the  class,  and  later 
they  may  be  repeated  by  the  pupils  at  home  or  at 
school. 

Reviews  and  Summaries.  —  At  the  beginning  of  each 
chapter  that  introduces  a  new  and  related  subject  there 
is  a  paragraph  reviewing  briefly  what  has  been  taught 
in  the  preceding  chapters,  and  showing  the  relation 
which  this  new  chapter  bears  to  the  old  and  familiar. 
This  facilitates  still  more  the  organization  of  the  facts 
of  this  science  and  gives  them  their  proper  perspective. 
It  emphasizes,  by  embodying  in  the  plan  of  the  text, 
that  old  and  important  pedagogical  principle,  "  From 
the  known  to  the  related  unknown."  Each  chapter 
closes  with  a  brief  summary  of  the  main  points  to 
be  remembered.  Such  reviews  and  summaries  are 
absolutely  essential  to  a  mastery  of  the  subject.  A 
very  common  mistake  in  teaching  this  subject  is  to 
permit  the  related  facts  necessary  to  an  intelligent 
understanding  of  the  new  lesson  or  new  topic  to  fade 
out  of  the  mind  entirely.  A  systematic  arrangement  of 


x  PLAN   OF  THE   BOOK 

topics,  reviews,  and  summaries  will  do  much  to  improve 
the  character  of  the  teaching  in  physiology. 

Gradation  of  Subject-matter.  —  There  is  a  steady,  but 
well-graded,  progress  from  the  easy  and  simple  to  the 
more  difficult  and  complex,  both  in  the  mode  of  treat- 
ment and  in  the  arrangement  of  the  topics.  On  the 
whole,  the  facts  presented  in  this  text-book  may  be  a 
little  more  difficult  than  those  found  in  most  of  the 
physiologies  for  corresponding  grades,  but  the  sen- 
tences are  short,  the  language  clear  and  simple,  the 
treatment  logical  and  connected,  the  illustrations  nu- 
merous, and  the  reviews  and  summaries  frequent,  so 
that  the  book  will  not  seem  difficult  to  the  pupils. 


ACKNOWLEDGMENTS 

MOST  of  the  drawings  for  this  book  were  made  by 
students  in  my  classes  at  the  Normal  School.  Two  of 
the  plates  were  kindly  furnished  by  the  Educational 
Review,  one  by  Ginn  &  Company,  and  several  by  The 
Macmillan  Company.  Due  credit  is  given  under  each 
figure. 

A  number  of  physicians,  superintendents,  principals, 
and  teachers  of  physiology  read  parts  or  all  of  the 
manuscript,  and  I  am  greatly  indebted  to  them  for 
many  helpful  suggestions  and  criticisms. 

I  am  also  indebted  to  Professor  W.  S.  Watson,  of  the 
State  Normal  School,  Whitewater,  Wisconsin,  to  Pro- 
fessor C.  E.  Patzer,  of  Milwaukee,  and  to  Mr.  Lewis 
C.  Sleeper,  of  Milwaukee,  for  rendering  valuable  assist- 
ance in  the  proof  reading;  and  to  Miss  Delia  G.  Ovitz, 
Librarian,  State  Normal  School,  Milwaukee,  for  pre- 
paring the  .index. 

JOHN  I.  JEGI. 

STATE  NORMAL  SCHOOL,  MILWAUKEE, 
June,  1903. 


CONTENTS 


CHAPTER   I 

INTRODUCTION 

Why  we  should  study  the  Human  Body  —  The  Human  Body 

—  Anatomy —  Physiology  —  Hygiene — The  Amoeba — The  Cell 

—  Some  Definitions  —  The  Body  compared  to  a  City  —  Order 
of  Topics  —  Summary  of  the  Main  Points. 


CHAPTER   II 

THE  BLOOD  AND  THE  LYMPH n 

Cell  Medium  —  Uses  of  the  Blood  —  What  Blood  looks  like 
—  Composition  of  Blood  —  Quantity  —  Clotting  —  Anaemia  — 
How  to  keep  the  Blood  Pure  and  Wholesome  —  Summary  of 
the  Main  Points. 


CHAPTER   III 

FOODS 17 

Definition  of  Foods  —  Kinds  of  Foods  —  Proteids — Carbo- 
hydrates —  Fats  —  Water  —  Salts  —  Oxygen  —  Substances  taken 
with  Foods  —  Animal  Foods  —  Vegetable  Foods  —  Hygiene  — 
Value  of  Cooking  —  Amount  of  Food  —  Summary  of  the  Main 
Points. 


CHAPTER  IV 

DRINKS  AND  NARCOTICS 3° 

Pure  Water  —  Impure  Water  —  Tea  and  Coffee  —  Milk  —  Alco- 
hol—  Alcoholic  Drinks  —  Alcohol  as  a  Food  —  The  Appetite  for 
Alcohol  —  Tobacco  —  Cigarettes  —  Summary  of  the  Main  Points. 


CONTENTS 


CHAPTER  V 

PAGE 

RESPIRATION 40 

Review — The  Air  Passages — The  Nose  —  The  Pharynx  and 
Larynx  —  The  Trachea  and  Bronchial  Tubes  —  The  Lungs  — 
Covering  of  the  Lungs  —  How  Air  gets  into  the  Lungs  —  Capacity 
of  the  Lungs  —  How  Air  gets  into  the  Blood  —  Changes  in  the 
Air  —  Rate  of  Breathing  —  Summary  of  the  Main  Points. 


CHAPTER   VI 

HYGIENE  OF  RESPIRATION 59 

Disease  Germs  in  the  Air  —  Diseases  of  the  Air  Passages  — 
Sources  of  Impure  Air  —  The  Air  purified  —  Ventilation  — 
Method  of  Ventilation  —  Chest  Freedom  —  Proper  Breathing 
—  Alcohol  —  Summary  of  the  Main  Points. 


CHAPTER  VII 

DIGESTION 72 

Review  —  The  Alimentary  Canal  —  Glands  —  The  Mouth  — 
The  Teeth  —  Structure  of  the  Teeth  —  Mouth  Digestion  — 
Swallowing  —  Stomach  Digestion  —  Intestinal  Digestion  — 
Places  of  Digestion  —  Peristalsis  —  Summary  of  the  Main  Points. 


CHAPTER  VIII 

FROM  THE  ALIMENTARY  CANAL  TO  THE  HEART     ....      96 

Review  —  Absorption  —  Absorption  of  Fats  —  The  Other 
Foods  — The  Liver  — Foods  in  the  Right  Heart  — The  Large 
Intestine  —  Summary  of  the  Main  Points. 


CHAPTER   IX 

HYGIENE  OF  DIGESTION  AND  ABSORPTION 105 

Pure  Foods  —  Adulterated  Foods  —  Cooking  —  Care  of  Teeth 

—  The  Appetite  —  Hygiene  of  Eating  —  Dress  and  Digestion 

—  Diseases  of  the  Alimentary  Canal  —  Alcohol  and  Digestion  — 
The  Large  Intestine  —  Summary  of  the  Main  Points. 


CONTENTS  xv 

CHAPTER  X 

PAGE 

CIRCULATION  OF  THE  BLOOD  119 

Review  —  The  Heart  —  Valves  and  Openings  of  the  Heart  — 
Blood  Vessels  — Lymphatics  —  Course  of  the  Blood  —  Rate  of 
Blood  Flow — What  makes  the  Blood  move  —  The  Heart  Beat 
—  Sounds  of  the  Heart  —  The  Pulse  —  Alcohol  and  Tobacco  — 
Summary  of  the  Main  Points. 

CHAPTER   XI 

FOODS  IN  THE  TISSUES 140 

Review — The  Lymph  —  The  Cell  —  Th 2  Wastes — Changes 
in  the  Blood  —  Animal  Heat  —  Loss  of  Heat  —  Regulation  of 
Temperature  —  Summary  of  the  Main  Points. 

CHAPTER   XII 

THE  SKIN  AND  THE  KIDNEYS 149 

Review  —  The  Skin  —  Glands  of  the  Skin  —  Appendages  of 
the  Skin  —  Care  of  the  Skin  —  Bathing  —  Clothing  —  The  Kid- 
neys—  Diseases  of  the  Kidneys  —  The  Effect  of  Alcohol  upon 
the  Skin  and  Kidneys  —  Summary  of  the  Main  Points. 


CHAPTER  XIII 

BONES  AND  JOINTS 167 

Uses  of  Bones  —  The  Skeleton  —  Table  of  Bones  —  Compo- 
sition of  Bone  —  Structure  of  Bone  —  Cartilage  —  Joints  — 
Posture — The  Curved  Spine  and  Round  Shoulders — Summary 
of  the  Main  Points. 

CHAPTER    XIV 

MUSCLES  AND  EXERCISE 189 

Uses  of  Muscles — 'Description  of  Muscles — Structure  of 
Muscles  —  How  Muscles  work  —  Large  Muscles  —  Food  of 
Muscles  —  Value  of  Exercise  —  Amount  of  Exercise  —  Physical 
Training  in  our  Schools  —  Time  of  Exercise  —  Fatigue  and 
Rest  —  Massage  —  Alcohol  and  Tobacco  —  Summary  of  the 
Main  Points. 


xvi  CONTENTS 

CHAPTER   XV 

PAGE 

SPECIAL  USES  OF  MUSCLES 207 

Review  —  Bones  as  Levers — Standing  —  Walking  and  Run- 
ning—  Muscles  of  Expression — The  Larynx  and  its  Use — Voice 
Sounds  —  Care  of  the  Voice  —  Summary  of  the  Main  Points. 

CHAPTER   XVI 

THE  NERVOUS  SYSTEM     .        .        . 219 

Plan  of  the  Nervous  System  —  Nerve  Tissue  —  The  Nerves  — 
The  Spinal  Cord  —  The  Brain  —  The  Bulb  —  The  Cerebellum  — 
The  Cerebrum  —  The  Sympathetic  Nervous  System  —  Mind  and 
Brain  —  Summary,  of  the  Main  Points. 

CHAPTER   XVII 

CARE  AND  TRAINING  OF  THE  NERVOUS  SYSTEM      ....    239 

Food  and  Air  —  Exercise  —  Education  —  Habit  —  P^atigue 
and  Overwork  —  Rest  and  Sleep  —  Alcohol  —  Tobacco  —  Sum- 
mary of  the  Main  Points. 

CHAPTER   XVIII 

THE  SPECIAL  SENSES  AND  SENSATIONS    .        .        .-       .        .        .253 

Sensations  —  General  Senses  —  The  Sense  of  Touch  —  The 
Sense  of  Taste  — The  Sense  of  Smell  — The  Sense  of  Hearing  — 
The  External  Ear — The  Middle  Ear  —  The  Inner  Ear  —  The 
Course  of  a  Sound  Wave  —  Care  of  the  Ear  —  The  Sense  of 
Sight — The  Eyeball  —  Muscles  of  the  Eye  —  Appendages  of  the 
Eye  — The  Inside  of  the  Eyeball  — The  Course  of  Light  — De- 
fective Vision  —  Care  of  the  Eyes  —  Summary  of  the  Main  Points. 

CHAPTER   XIX 

BACTERIA  AND  DISEASES 279 

Bacteria  —  Bacteria  as  our  Friends  —  Bacteria  as  Enemies  — 
How  Disease  Germs  get  into  the  Body  —  Disease  Germs  in  the 
Body  —  Consumption  —  Pneumonia  —  Cholera  —  Typhoid  Fever 
—  Dysentery  —  Diphtheria  —  Scarlet  Fever  —  Measles  —  Small- 
pox —  Mumps  —  Whooping  Cough  —  Malarial  Fever  —  Yellow 
Fever  —  Grippe  —  Pink  Eye  —  Summary  of  the  Main  Points. 


CONTENTS  xvii 

CHAPTER  XX 

PAGE 

PUBLIC  HEALTH  AND  PERSONAL  HYGIENE 299 

The  Problems  —  Public  Intelligence  —  Fouus  —  Water  Supply 

—  The  Air  —  Garbage  —  Cleanliness  —  Diseases  —  Schools  and 
Diseases  —  Disinfection  —  Personal  Hygiene  —  Summary  of  the 
Main  Points. 

CHAPTER   XXI 

FIRST  AID  IN  ACCIDENTS  AND  EMERGENCIES 315 

Introduction  —  Burns  and  Scalds  —  Sunstroke  —  Fainting  — 
Suffocation  —  Choking  —  Apparent  Drowning  —  Fits  —  Bruises 

—  Frost  Bite  —  Poisonous  Stings  —  Poisons  —  Sprains  —  Dislo- 
cations—  Broken  Bones  —  Cuts  in  the  Skin  —  External  Bleeding 

—  Nose  Bleeding — Lung  and  Stomach  Bleeding — Sore  Throat. 

GLOSSARY 3-5 

INDEX .    337 


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V*ll/, 


PRACTICAL    LESSONS 

IN 

HUMAN    PHYSIOLOGY 

CHAPTER   I 

INTRODUCTION 

1.  Why  we  should  study  the  Human  Body.  —  We  all 

wish  to  become  strong,  useful,  and  happy  members  of 
society.  In  order  that  this  goal  may  be  reached  it  is 
necessary  to  properly  care  for  our  bodies.  We  must 
learn  early  to  habitually  do  those  things  which  will 
make  the  body  strong,  robust,  and  healthy,  and  to  avoid 
all  those  things  which  tend  to  hinder  growth,  enfeeble 
the  body,  and  cause  disease. 

The  human  body  is  a  wonderful  machine  that  must 
be  understood  if  it  is  to  serve  its  purpose  best.  This 
book  attempts  to  explain  in  a  simple  way  these  bodies 
of  ours,  and  to  teach  us  how  to  care  for  them  properly 
in  health,  and  how  to  prevent  disease. 

2.  The  Human  Body.  —  We  all  know  that  the  body 
consists  of  the  head,  arms,  trunk,  and  legs;    that  it  is 
covered  with  skin,  and  that  it  is   made   up   of   bones, 
muscles,   nerves,  blood,   etc.     We   know  that   the  dif- 


2  HUMAN  PHYSIOLOGY  CHAP. 

ferent  parts  of  the  body  are  under  our  control.  We 
can  move  the  head,  hands,  feet,  and,  in  fact,  the  entire 
body  at  our  pleasure.  The  bones  are  moved  by  the 
muscles*  which  are  controlled  by  the  nerves  that  carry 
the  messages  sent  out  by  the  mind. 

In  some  respects  the  body  may  be  compared  to  a 
locomotive.  The  locomotive  consists  of  a  furnace,  a 
boiler,  a  piston,  wheels,  levers,  etc.,  while  the  body  has 
bones,  muscles,  a  heart,  a  stomach,  a  brain,  etc.,  as  its 
machinery.  Coal  and  wood  are  put  into  the  furnace, 
while  meats,  potatoes,  bread,  etc.,  are  taken  into  the 
stomach,  and  serve  as  fuel.  The  heat  from  the  coal 
changes  the  water  in  the  boiler  to  steam,  which  is  the 
motive  power  that  turns  the  wheels  and  moves  the  train 
along  the  track.  The  foods  taken  into  the  stomach  and 
changed  to  blood  are  burned  in  the  cells  of  the  body. 
The  heat  thus  produced  serves  to  keep  us  warm  and  to 
keep  in  operation  the  machinery  of  the  human  body. 
The  body  differs  from  the  locomotive  in  that  it  is  self- 
oiling,  self-repairing,  and  self -increasing  in  size,  —  some 
of  the  foods  serving  these  purposes.  Beautiful  and 
wonderful  as  is  the  most  complicated  machine  ever  in- 
vented by  man,  the  body  exceeds  it  in  beauty  of  form, 
delicacy  of  adjustment,  and  complexity  of  organization. 

The  study  of  the  human  body  is  one  of  the  most 
interesting  and  useful  branches  taught  in  our  schools. 
We  call  this  study  human  anatomy,  pJiysiology,  and 
hygiene. 

3.  Anatomy.  —  The  science  which  treats  of  the  gross 
structure  of  the  body,  i.e.  the  shape,  size,  and  location  of 


i  INTRODUCTION  3 

the  various  parts,  is  called  human  anatomy.  The  body 
is  made  up  of  many  different  parts  called  organs,  as  the 
heart,  liver,  stomach,  eyes,  etc.  The  clock  in  the  room 
has  hands,  a  case,  a  dial,  a  mainspring,  etc.  These  are 
all  facts  of  anatomy.  Can  you  mention  others  ?  Give 
something  of  the  anatomy  of  a  jackknife,  of  a  school 
desk,  of  a  shoe. 

4.  Physiology.  —  The  science  which  deals  with  the 
uses  or  functions  of  the  various  parts  of  the  body  is  called 
human  physiology.     The  teeth  are  for  the  purpose  of 
cutting  and  grinding  foods ;  the  stomach  helps  to  pre- 
pare foods  for  the  blood ;  and  the  skin  serves  to  protect 
the  body  from  foreign  objects.     The  hands  of  the  clock 
indicate  the  time  of  day ;    the  key  is  for  winding  the 
clock ;    and  the  case  contains  the  works  and   protects 
them  against  dust  and  other  harmful  substances.     These 
are  facts  of  physiology. 

5.  Hygiene.  —  The  science  which  deals  with  the  care 
of  the  various  parts  of  the  body  or  with  the  laws  of  health 
is  called  personal  hygiene.     The  teeth  should  be  prop- 
erly cleaned  daily ;    our  meals  should  occur  at  regular 
intervals  and  at  the  same  hour  each  day ;    the  foods 
should  be  well  cooked  and  thoroughly  chewed ;  and  the 
skin  should  be  kept  clean  by  frequent  bathing.     The 
clock  should  be  wound  at  the  same  time  daily ;  and 
should  be  kept  in  a  dry,  clean,  safe  place.     These  are 
statements  of  hygiene. 

We  shall  learn  in  this  book  many  of  the  important 
laws  of  health,  so  that  we  shall  be  able  to  do  those 
things  which  will  make  us  strong  and  keep  us  well. 


4  HUMAN   PHYSIOLOGY  CHAP. 

We  shall  learn  something  of  public  health  or  of  the 
laws  that  relate  to  the  well-being  of  people  living  in 
towns,  villages,  and  cities.  There  are  laws  of  public 
health  as  well  as  of  personal  hygiene. 

6.  The  Amoeba.  —  In  water  and  moist  earth  there  live 
animals  so  small  that  they  can  be  seen  only  with  the  aid 
of  a  microscope.  The  amoeba  belongs  to  one  of  these 
classes.  It  looks  when  highly  magnified  like  a  bit  of 
jelly.  No  one  who  does  not  watch  it  closely  for  a  long 
time  would  believe  that  it  is  a  live  animal.  It  is  so 
simple  in  structure  that  it  is  without  mouth,  head,  legs, 
or  stomach,  and  yet  it  has  the  power  to  move  about  in 


FIG.  i.  —  Amoebas  as  seen  under  the  microscope  (Buchholz). 

the  water,  to  breathe,  and  to  eat.  When  the  amoeba 
has  grown  to  full  size  it  divides  and  forms  two  tiny 
amoebas,  each  having  all  the  power  of  the  parent.  The 
amoeba  is  a  tiny  bit  of  living  matter  called  protoplasm. 

Place  under  the  microscope  a  drop  of  water  taken  from  a  stagnant 
pond,  or  from  a  barrel  of  rain  water  that  has  become  somewhat  slimy.. 
Examine  it  very  carefully  for  amoebas.  Make  a  drawing  of  what  you 
see. 

7.  The  Cell.  —  Our  bodies  are  very  complex  in 
structure,  being  made  up  of  numerous  parts  or  organs 
which  do  not  look  at  all  alike.  Each  of  these  parts  is 
composed  of  many  small  bits  of  living  matter  called 


INTRODUCTION 


5 


cells.  The  amceba  is  a  single  cell,  but  our  bodies  con- 
sist of  millions  upon  millions  of  cells,  each  of  which  is 
a  living  particle 
like  the  amoeba. 
Every  cell  in  the 
body  takes  in 
foods  and  gives  off 
wastes  ;  it  may  be 
said  then  that  it 
eats  and  breathes. 


l/acuole 
Food 


The  cells  of  the 

human  body  vary       FIG.  2.  — Atypical  cell.     Modified  from  Wilson 
7  ,  (Zinns). 

in  size,  shape,  and 

consistency.  Some  are  small,  globular  masses,  some  are 
thin,  flat,  or  scaly,  and  others  are  long,  slender,  and  very 
irregular.  Some  are  very  soft  and  like  jelly,  while 
others  are  hard,  firm,  and  like  bone.  Each  cell  has  a 

special  use,  and 
its  size  and  shape 
are  such  as  to  fit 
it  to  best  per- 
form its  func- 
tion. Although 
the  cells  differ 
widely  from  one 
1 * MUSCle  cells  another  in  ap- 
pearance and 

FIG.  3.  —  Various  cells  of  the  body  (Zinns).  \\$>Q    theV  are  all 

composed  chiefly  of  water  (about  three  fourths),  a  sub- 
stance quite  like  the  white  of  an  egg,  called  proteid, 


6  HUMAN   PHYSIOLOGY  CHAP. 

some  sugar  and  starch,  fats,  and  salts.  These  little 
masses  are  held  in  place  by  fine  threads  or  fibers  known 
as  connective  tissue. 

Scrape  the  moist  lip  lightly  with  a  knife  and  place  the  mass  under 
the  microscope.  Try  to  find  very  light,  flat,  irregular  scales.  These 
are  scaly  cells.  Make  a  drawing. 

8.  Some  Definitions. 

1.  A  cell  is  any  mass  of  living  matter  containing  a 
nucleus. 

2.  A  tissue  is  a  collection  of  similar  cells  having  the 
same    functions,   as  bony  tissue,    nerve   tissue,    muscle 
tissue,  and  fat  or  adipose  tissue. 

3.  An  organ  is  a  collection  of  several  tissues  arranged 
in    some    definite    and  compact  way  to   perform   some 
special  function,  as  the  heart,  lungs,  liver,  and  eye. 

4.  A   system  is  a  group  of    several  organs  that  aid 
each  other  in  doing  the    same  kind  of    work,    as   the 
nervous,  muscular,  and  digestive  systems. 

5.  An   organism   is  a  collection  of    all   the  systems 
necessary  to  carry  on  the  life  processes,  as  man,  dog, 
fish,  and  oyster. 

9.  The  Body  compared  to  a  City.  —  A  city  consists  of 
hundreds    of    human   beings   all  dependent  upon    one 
another,  each  having  his  desires   and  wants  and  con- 
tributing his  share  to  the  common  good.     Trains,  boats, 
and  wagons  are  busy  carrying  food,  fuel,  and  luxuries 
to    supply  the   needs   and    satisfy  the   wants   of    each 
individual   in    the    city.     The   city    depends    upon   the 
surrounding  country,  upon  other  cities,  and  more  or  less 
upon  the  rest  of  the  world.     Water  is  piped  into   the 


I  INTRODUCTION  7 

city  and  carried  into  the  various  rooms  of  every  house. 
Pipes  from  the  houses  convey  the  sewerage  from  the 
city  into  a  lake  or  river,  and  wagons  gather  up  the 
garbage  and  ashes  from  every  house.  Have  you  ever 
thought  what  a  problem  it  is  to  feed  a  city  and  to 
remove  its  wastes  ?  It  is  not  the  city  as  a  whole  but 
each  individual  person  of  the  city  that  must  be  fed, 
clothed,  sheltered,  and  cared  for.  Each  person  has 
needs  that  must  be  supplied  and  wants  that  must  be 
satisfied. 

The  human  body  consists  of  millions  of  cells,  each 
having  its  wants  and  doing  its  share  for  the  common 
good.  They  all  depend  upon  one  another.  The  food 
which  is  taken  into  the  mouth  reaches  the  stomach, 
and,  finally,  the  blood.  It  must,  however,  be  carried  to 
the  individual  cells  all  over  the  body.  The  blood  con- 
veys the  foods  to  the  cells  and  removes  the  waste  prod- 
ucts from  them.  It  is  not  the  body  as  a  whole  but 
each  and  every  living  cell  that  must  receive  food,  be 
kept  warm,  and  have  its  wastes  removed,  so  that  it  may 
properly  do  its  share  of  work. 

The  cells  of  the  body  correspond  to  the  individuals  of 
the  city.  Each  cell  is  a  living  unit,  having  its  needs  and 
doing  its  work.  That  is  the  important  thing  to  remem- 
ber in  studying  physiology.  As  we  learn  more  about  the 
human  body  this  comparison  will  be  clearer. 

10.    Order  of  Topics. 

i.  We  shall  first  study  the  blood  which  receives  the 
food  and  conveys  it  to  the  cells,  and  which  carries  away 
from  the  cells  their  wastes  and  removes  them  from  the 


8  HUMAN   PHYSIOLOGY  CHAP. 

body.     Blood  is  the  liquid  upon  which  the  life  and  well- 
being  of  each  cell  depend. 

2.  Then  we  shall  see  what  the  different  foods  are, 
where  they  come  from,  and  how  they  are  prepared  for 
the  blood. 

3.  Next  we  shall  study  water  and  other  drinks  taken 
with  our  meals.     Tobacco  and  other  narcotics  will  be 
treated  in  the  same  chapter. 

4.  We  shall  then  learn  how  oxygen  of  the  air  gets 
into  the  blood.     This  will  be  studied  under  Respiration. 

5.  Under  Digestion  and  Absorption  we   shall  learn 
how  the  solid  and  liquid  foods  are  dissolved  and  taken 
into  the  blood. 

6.  After  we  have  learned  how  the  foods  and  oxygen 
get  into  the  blood  we  shall   study   Circulation   to  see 
how  the  blood  is  carried  to  the  cells  in  all  parts  of  the 
body. 

7.  In  the  chapter  on  Foods  in  the  Tissues  we  shall 
learn  how  the  various  things  we  eat  and  drink  are  used 
by  the  cells,  and  how  the  cells  grow,  keep  warm,  and 
do  their  work. 

8.  We  shall  then  study  the  skin  and  the  kidneys  to 
see  how  the  heat  of  the  body  is  regulated,  and  how  the 
waste  products  are  removed  from  the  blood  and  elim- 
inated from  the  body. 

9.  The  bones  and  muscles  will  next  be  studied  to 
learn  what  the  framework  of  the  body  is  and  how  the 
muscles  act  on  the  bones  to  produce  motion  and  to  do 
work.     In    this    connection  we    shall  also    study  voice 
and  speech. 


i  INTRODUCTION  9 

10.  The  nervous  system,  which  controls  all  parts  of 
the  body  and  forms  the  organ  of  the  human  mind,  will 
be  treated  next. 

n.  In  close  relation  to  the  nervous  system  stand  the 
sense  organs  that  enable  us  to  see,  hear,  taste,  smell, 
and  feel. 

12.  We  shall  then  study  some  of  the  more  common 
diseases  to  see  how  they  are  caused,  how  they  spread, 
and  how  they  may  be  warded  off. 

13.  This  will   be    followed   by  a  chapter  on    public 
health  and  personal  hygiene,  based  on  our  knowledge 
of  the  human  body  as  learned  in  studying  this  book. 

This  order  of  topics  we  shall  find  easy  to  follow,  for 
it  is  a  very  natural  way  of  studying  the  human  body. 
It  will  make  the  whole  subject  easy  to  understand,  and 
at  the  same  time  very  interesting,  because  one  thing 
grows  right  out  of  another. 

SUMMARY   OF  THE   MAIN   POINTS 

1.  A  study  of  the  human  body  will  enable  us  to  understand 
its  parts,  how  they  work,  and  how  to  keep  well. 

2.  The  human  body  is  a  very  complex  organism,  being  com- 
posed of  many  parts,  each  having  its  own  needs  and  doing  its 
own  work  for  the  common  good.     It  is  a  wonderful  machine. 

3.  Anatomy  is  the  science  which   deals  with  the  gross  or 
general  structure  of  the  human  body. 

4.  Physiology  is  the  science  which  deals  with  the  uses  of 
the  different  parts  of  the  body. 

5.  Hygiene  is  the  science  and  art  of  health.     It  tells  how  to 
get  well,  and  how  to  keep  the  body  in  a  healthy  condition  all 
the  time. 


io  HUMAN   PHYSIOLOGY  CHAP,  i 

6.  A  cell  is  any  small  mass  of  living  matter  containing  a 
nucleus.     It  is  the  unit  of  structure  and  function  in  both  ani- 
mal and  plant  life. 

7.  The  human  body  consists  of  millions  of  cells,  each  of 
which  must  have  food  to  keep  it  alive  and  in  good  working 
condition. 

8.  In  some  respects  the  life  and  activity  of  each  cell  may  be 
compared  to  that  of  an  individual  person  in  a  large  city. 

9.  It  is  important  to  remember  that  each  cell  in  the  human 
body  is  a  living  unit,  having  its  own  needs  and  doing  its  own 
work. 

10.  The  human  body  is  made  up  of  several  systems;  each 
system  is  composed  of  organs ;  every  organ  is  constructed  out 
of  tissues  j  and  a  tissue  in  turn  is  made  up  of  cells. 


CHAPTER   II 

THE   BLOOD    AND    THE   LYMPH 

11.  Cell  Medium.  —  We  learn  that  the  amoeba  moves 
about  in  water  from  which  it  obtains  its  food  and  to 
which  it  gives  off  its  wastes.  Each  living  working  cell 
of  our  bodies  lives  in  a  liquid  called  lymph.  The  cells 
cannot  move  about  in  search  of  food,  and  so  lymph  con- 
taining all  the  foods  necessary  for  the  cells  is  brought 
to  them  by  the  blood  as  it  circulates  to  all  parts  of  the 
body.  Lymph  is  a  liquid  that  is  found  in  all  parts 
of  the  body:  in  fingers  and  toes,  in  heart  and  lungs, 
in  stomach  and  liver,  in  muscles  and  bones.  It  is  so 
generally  distributed  that  every  cell  is  surrounded 
by  a  small  amount  of  lymph,  just  as  the  amoeba  is  sur- 
rounded by  water.  If  we  put  a  sponge  in  water,  it 
will  take  up  the  liquid  until  it  is  completely  rilled. 
Now  if  we  place  the  sponge  on  the  table,  we  cannot  see 
the  water  within  it,  and  yet  we  know  that  every  tiny 
particle  of  sponge  is  moist,  and  is  bathed  in  water.  In 
a  very  similar  way  the  lymph  permeates  the  human 
body  and  comes  in  contact  with  each  and  every  cell. 

The  cells  get  their  nourishment  directly  from  the 
lymph  and  give  off  their  waste  materials  and  worn-out 
parts  to  it.  The  blood  supplies  the  lymph  ivith  food 


12  HUMAN  PHYSIOLOGY  CHAP. 

materials  for  the  cells,  and  removes  from  it  the  waste 
products  of  tJie  cells. 

12.  Uses  of   the   Blood.  —  All  the   foods  we   eat  are 
changed  in  the  body  so  that  they  become  part  of  the 
blood,  and  may  be  used  to    keep  the  cells  in  a  good, 
healthy  condition.     The  water  we  drink  also  gets  into 
the  blood  and  is    carried    to    the   cells,  where  it  is  of 
great  use.     Even  the  air  we  breathe  finds  its  way  into 
the  blood,  which  then  carries  the  oxygen  to  the  cells 
throughout  the  body.     Thus  we  see  that  the  blood  brings 
oxygen  and  foods  together  in  the  cells  in  all  parts  of 
the  body.     The  chief  function  of  the  blood  is  to  carry 
foods  and  wastes.     The  blood  is  necessary  to  keep  us 
alive ;    to  keep  us  well ;   to  give  us  strength  to  work ; 
and  to  make  us  grow. 

13.  What  Blood  looks  like.— We  have  all  seen  blood 
and  know  that  it  is  a  bright  red  liquid.     Through  a  mi- 
croscope it  is  not  red  at  all  but  yellow  in  color.     The 
whole  mass  of  water  of  a  large  lake  looks  blue,  but  a 
small  amount  does   not.     And   it   is  just    so   with   the 
blood ;  a  drop   looks  red,  but  a  very  small  amount  as 
seen  under  the  microscope  looks  pale  yellow. 

Prick  yourself  with  a  sharp,  clean  needle  so  as  to  draw  a  small 
drop  of  blood.  Examine  it  with  a  microscope.  Describe  what  you 
find.  The  small  masses  are  red  blood  corpuscles  floating  about  in 
the  plasma.  Do  you  see  larger  white  masses  ?  They  are  white 
corpuscles. 

14.  Composition    of    Blood.  —  Under  the  microscope 
we  see  thousands  of  tiny  yellow  bodies  moving  about 
in  a  colorless  liquid.     These  solids,  oddly  enough,  are 


THE  BLOOD  AND  THE  LYMPH 


called  red  corpuscles.  They  are  about  one  thirty-two 
hundredth  of  an  inch  in  diameter,  and  so  numerous  that 
a  single  small  drop  contains  about  five  millions  of  them. 
We  also  find  white  corpuscles,  a  little  larger  than  the  red, 
but  they  are  not  nearly  as  numerous. 


1111 


Reef  corpuscles 


Mite  corpuscles 


FIG.  4. —  Human  blood  corpuscles  (Zinns). 

The  colorless  liquid  in  which  the  corpuscles  float 
about  is  called  plasma.  Plasma  is  water  containing  in 
solution  the  foods  that  have  been  changed  into  blood  and 
also  the  wastes  of  tJie  cells. 

What  are  the  corpuscles  for  ?  The  red  corpuscles  are 
very  numerous  and  surely  must  be  of  great  value.  //  is 
tJie  red  corpuscles  that  have  the  power  to  carry  oxygen  from 
tJie  lungs  to  all  the  cells  of  the  body.  This  is  their  only 
use,  and  an  important  office  it  is.  They  are  busy  day 
and  night,  doing  all  they  can  to  keep  the  cells  supplied 
with  oxygen.  We  know  that  a  fire  in  a  stove  or  a  fur- 


i4  HUMAN   PHYSIOLOGY  CHAP. 

nace  will  not  burn  when  the  drafts  are  closed,  cutting 
off  the  supply  of  air.  Each  cell  in  the  body  is  a  little 
furnace  in  which  the  foods  we  eat  are  slowly  burned  up 
or  oxidized.  If  the  blood  contains  too  few  red  corpuscles, 
or  if  we  do  not  breathe  enough  oxygen,  the  fire  must  be 
low  in  the  cells. 

TJie  white  corpuscles  are  said  to  have  the  poiver  to 
destroy  disease  germs  and  to  pick  out  poisons  that  get 
into  the  blood,  and  so  they  tend  to  keep  the  blood  pure 
and  wholesome.  They  are  thought  to  aid  in  blood- 
clotting,  and  they  doubtless  have  other  functions. 

15.  Quantity.  — About  one  thirteenth  of  the  weight  of 
the  body  is  blood.     A  person  weighing  one  hundred  and 
fifty-six  pounds  would  have  about  twelve  pounds  of  blood. 
Of  course,  the  amount  varies  in  different  persons.      TJie 
exact   amount   of  lymph    is   unknown,   but   it   is    much 
greater  than  that  of  the  blood. 

One  fourth  of  the  blood  is  in  the  lungs,  heart,  and  large 
blood  vessels  ;  one  fourth  in  the  liver  ;  one  fourth  in  the 
small  blood  vessels  of  the  muscles  and  skin ;  and  one 
fourth  in  the  various  other  organs  of  the  body. 

16.  Clotting.  —  When  the  blood  is  exposed  to  the  air, 
little   threads   called   fibers   form    in  the    plasma,  that 
entangle  the  corpuscles  and  form  a  solid  mass  called  a 
clot.     The  fibers  that  form  throughout  the  entire  mass 
are  made  of  a  substance  called  fibrinogen,  that  is  found 
in  the  plasma.     By  the    contraction  of   these  fibers,  a 
yellowish  watery  fluid  called  serum  is  squeezed  out  of 
the  solid  mass  in  which    the    clot  then  floats.     Blood 
minus  the  clot  equals  blood  serum. 


ii  THE   BLOOD   AND   THE   LYMPH  15 

Clotting  is  of  great  value  as  a  means  of  preventing 
bleeding  to  death  from  wounds.  The  clot  forms  a  plug 
that  closes  the  opening  of  a  blood  vessel. 

Get  a  tumbler  half  full  of  fresh  blood  and  leave  it  exposed  to  the 
air  for  a  short  time.  Watch  it  carefully  and  describe  the  formation 
of  the  blood  clot.  The  yellowish  liquid  that  is  squeezed  out  is 
the  serum. 

17.  Anaemia.  —  Blood  may  contain  red  corpuscles  so 
poorly  made  or  so  few  in  number  that  they  are  unable  to 
carry  a  sufficient  amount  of  oxygen  to  the  cells  of  the 
body.     Such  a  condition  is  known  as  ancemia.     A  per- 
son who  is  anaemic  is  languid,  pale  in  the  face,  lips,  and 
under  the  finger  nails.     He  complains  that  he  is  tired 
after  the  slightest  exercise,  and  suffers  much  from  head- 
ache and  drowsiness. 

18.  How  to  keep  the  Blood  Pure  and  Wholesome. 

1.  Eat  an  abundance  of  good,  wholesome  food  daily. 

2.  Work  and  sleep  in  rooms  thoroughly  ventilated. 

3.  Take  a  sufficient  amount  of  outdoor  exercise  in 
the  sunshine  each  day. 

4.  Keep  the  clothing  loose,  so  as  not  to  interfere  with 
the  circulation  of  the  blood  or  with  the  action  of  the 
lungs. 

5.  Keep  the  skin  clean  by  frequent  baths. 

6.  Never  drink  beverages  that  contain  alcohol,  whether 
in  large  or  small  quantities. 

7.  Get  enough  sleep  every  night  so  that  the  waste 
products  may  be  removed  from  the  blood  daily. 

8.  Remember  that  health  depends  largely  upon  the 
condition  and  quantity  of  the  blood. 


16  HUMAN   PHYSIOLOGY  CHAP,  n 


SUMMARY   OF  THE   MAIN   POINTS 

1.  Each  living,  working  cell  of  the  human  body  is  sur- 
rounded by  lymph  which  contains  the  food  for  the  cells,  and 
the  wastes  of  the  cells. 

2.  The  blood  receives  solid  foods,  water,  and  oxygen  and 
carries  them  to  the  lymph,  and  removes  from  the  lymph  the 
wastes  of  the  cells. 

3.  The  mass   color  of  blood  is  bright  red,  but  a  small 
amount  as  seen  under  a  microscope  is  pale  yellow. 

4.  The  blood  is  made  up  of  red  and  white  corpuscles  and 
plasma. 

5.  The  red  corpuscles  are  oxygen  carriers,  and  the  white 
ones  destroy  disease  germs  that  get  into  the  blood,  and  aid  in 
blood  clotting. 

6.  The  average  person  has  from  ten  to  twelve  pounds  of 
blood,  and  a  much  larger  quantity  of  lymph. 

7.  One  fourth  of  the  blood  is  in  the  heart,  lungs,  and  large 
blood   vessels ;    one    fourth  in  the   liver ;    one  fourth  in  the 
muscles  ;  and  one  fourth  in  the  other  organs. 

8.  The  blood  clots  when  exposed  to  the  air,  and  so  tends 
to  prevent  great  loss  of  blood  from  wounds. 

9.  Anaemia  is  due  to  a  lack  of  coloring  matter  in  the  blood. 
10.   The  general  health  depends  upon  the   condition  and 

amount  of  blood. 


CHAPTER    III 

FOODS 

19.  Definition  of  Foods.  —  We  have  learned  that  all 
the  cells  of  the  body  need  food  to  keep  them  well  and 
to  enable  them  to  do  their  work  properly.     We  have 
learned  that  the  blood  and  lymph  are  the  great  body 
liquids  from  which  each  cell  gets  its  food  and  to  which 
it  gives  off  its  wastes.      How  does  the  blood  get  its 
food  supply  ?     The  supply  in  the  blood  would  soon  be 
used  up  if  it  were  not  constantly  renewed  from  the  out- 
side.    We  eat,  drink,  and  breathe  to  furnish  the  blood 
proper  material  to  carry  to  the  cells  for  their  nourish- 
ment  and    use.      Not    all    substances    taken    into    the 
mouth  can  be  used  by  the  cells.     Some  are  not  only 
useless  but  harmful  and  even  poisonous. 

A  food  is  any  substance  that  enters  the  blood,  and  with- 
out doing  any  Jiarm  in  the  body  helps  to  cause  growth,  to 
repair  the  cells,  or  to  give  Jieat  and  mechanical  energy. 

20.  Kinds  of  Food.  —  The  body,  like  other  machines, 
wears  out  with  use,  but  differs  from  them  in  that  it  is 
self-increasing,  self-repairing,  and  self-oiling.     For  this 
pur-pose   it   needs  tissue-building  food  stuffs  known  as 
proteids.     The  locomotive   consumes   coal    to    produce 
the  heat  which  changes  the  water  to  steam,  and  the 

c  17 


1 8  HUMAN   PHYSIOLOGY  CHAP. 

body  needs  foods  to  furnish  the  heat  which  keeps  us 
warm  and  to  yield  the  energy  which  enables  us  to  work. 
The  chief  heat-producing  and  energy-yielding  food  stuffs 
are  called  carbohydrates  (starches  and  sugars]  and  fats. 

The  proteids,  carbohydrates,  and  fats  would  be  of  no 
value  to  the  cells  without  oxygen.  It  is  only  when 
coal  and  oxygen  are  made  to  combine  that  heat  is  pro- 
duced in  a  furnace,  and  likewise  no  burning  or  oxidation 
could  take  place  in  the  cells  without  an  abundant  supply 
of  oxygen. 

The  solid  food  stuffs  could  not  get  into  the  blood  nor 
to  the  cells  if  they  were  not  dissolved  in  water  and  car- 
ried along  by  water,  which  makes  up  a  large  part  of  the 
blood.  Salt  is  another  class  of  necessary  food  stuffs. 

TABLE  OF  FOOD  STUFFS 

1 .  Proteids,  the  building  foods. 

2.  Carbohydrates  1 

P  t  \  the  force  and  heat  producing  foods. 

4.  Water  1 

5.  Salts  \  important  aids  in  both. 

6.  Oxygen 

21.  Proteids.  —  They  form  the  only  class  of  foods  that 
contain  all  the  elements  necessary  to  cause  growth  arid  to 
repair  cells.  For  this  reason  proteids  are  absolutely 
necessary  to  maintain  life.  Eggs,  lean  meats,  cheese, 
beans,  peas,  lentils,  and  milk  are  among  the  common 
foods  that  belong  to  this  class.  Most  of  the  cereals,  as 
wheat,  barley,  oats,  and  corn,  contain  considerable  pro- 
teid.  This  is  the  kind  of  food  that  makes  muscle  and 
other  tissues.  We  would  starve  without  proteids. 


Ill 


FOODS 


Could     we    live     on     proteids 
alone  ?      Yes.      Yet  the  proteids 
do  not  form  an  ideal  food,  because 
they  are  not  easily  oxidized  in 
the  body,  and   so  are    not    as 
valuable  for  producing  heat  and 
energy  as  the  carbohydrates  and 
fats.      How  much  proteid,  then, 
should  we  eat  ?     The  answer  to 
this  question  is  simple.  We  should 
eat  just  enough  proteid  to  repair 
the  cells  properly  and   to   afford 
sufficient  material  for  growth. 

Obtain  five  cents'  worth  of  iodine 
from  a  drug  store  and  dilute  it  with  water 
until  it  shows  a  light  brown  color.  Label 
and  save  for  future  use. 

1.  Take  any  food  that  contains  pro- 
teid, as  lean  meat,  and  place  it  in  a  strong 
iodine  solution  for  a  short  time.     Notice 
how  brown  it  becomes.     What  do  you 
infer  ? 

2.  Try  the  white  of  an  egg  and  other 
proteids  in  the  same 


22.  Carbohydrates.  —  This  is  a 
very  large  class  of  food  stuffs,  in- 
cluding starches  and  sugars  ob- 
tained from  both  the  animal  and 
the  vegetable  kingdoms.  Most 
vegetables  are  rich  in  starches, 
as,  for  example,  wheat,  rye,  barley, 


FIG.  5.  —  Starch  as  seen  under 
the  microscope  (Buchholz) : 
A,  potato ;  B,  wheat  ; 
C,  corn  ;  and  D,  oats. 


20 


HUMAN   PHYSIOLOGY 


CHAP. 


oats,  rice,  potatoes,  tapioca,  etc.  Some  fruits  contain 
considerable  sugar.  Carbohydrates  are  heat  and  energy 
producing  foods  and  should  form  the  bulk  of  our  daily 
meals.  They  are  quite  easily  prepared  for  the  blood 
and  readily  oxidized  in  the  cells. 

1.  Take  a  little  common  starch  and  boil  it  for  a  few  minutes. 
Then  add  a  few  drops  of  iodine  solution.     Notice  the  characteristic 
blue  color. 

2.  Test  other  foods  that  contain  starch  in  a  similar  way. 

23.  Fats.  —  All  meats  and  nearly  all  vegetables  con- 
tain more  or  less  fat  and  oil,  so  it  is  really  impossible 

-  to  avoid  fats.  Pork, 

^  '  butter,  lard,  suet, 
olive  oil,  etc.,  are 
rich  in  fats  and 
oils.  Fats  are  very 
important  heat- 
producing  foods, 
but  they  are  not 
as  easily  digested 
as  proteids  or 
starches,  and  hence 
should  not  form  a 
very  large  part  of 
our  meals.  In  the 
winter  and  in  very 
cold  countries  people  eat  considerable  fats  and  oils. 

24.  Water.  —  When  we  remember  that  about  three 
fourths  of  the  human  body  is  water,  we  can  see  how 
important    it    must  be  as  a  food.      Nearly  everything 


FIG.  6.  —  Fat  meat  as  it  appears  under  the 
microscope  (Buchholz). 


in  FOODS  21 

that  we  eat  contains  more  or  less  water,  and,  besides, 
we  drink  water  freely  not  only  with  our  meals  but  at 
other  times.  All  common  beverages,  as  milk,  coffee, 
tea,  cocoa,  and  chocolate  are  almost  entirely  water. 

TABLE  SHOWING  THE  PERCENTAGE  OF  WATER  IN  SOME  FOODS 


Meat     .     . 

•     77 

Eggs     .     .     . 

74 

Milk  .     .     . 

.     88 

Potatoes    . 

.     76 

Carrots 

87 

Cabbage 

.     92 

Mushrooms 

.     90 

Fruit     .     .     . 

84 

Asparagus  . 

.     94 

Spinach 

.     92 

Cauliflower     . 

92 

Onions  .     . 

•     79 

Beets     .     . 

.     88 

String  beans  . 

94 

Tomatoes   . 

•     94 

Squash  . 

.     87 

Lettuce      .     . 

93 

Oysters  .     . 

.     87 

1.  Carefully  weigh  a  good-sized  fresh  potato.     Then  leave  it  in  a 
warm  place  for  a  few  days  and  watch  it  dry  up  slowly  until  there  is 
little  left.     Weigh  again.     The  loss  of  weight  is  due  to  the  loss  of 
water  by  evaporation. 

2.  Try  other  vegetables  in  a  similar  way.     If  the  vegetables  are 
sliced  thin,  the  evaporation  will  go  on  faster. 

Water  has  many  uses  in  the  body.  It  moistens  and 
dissolves  the  solid  foods  so  that  they  may  be  easily 
swallowed  and  taken  into  the  blood.  The  blood  itself  is 
over  eighty  per  cent  ivater.  It  holds  in  solution  all  the 
solid  foods  and  carries  along  the  corpuscles  of  the 
blood.  The  lymph  around  the  cells  has  a  larger  pro- 
portion of  water.  The  cells  of  the  body  are  nearly  eighty 
per  cent  ^vater.  The  wastes  of  the  cells  are  dissolved  in 
water  and  so  removed  from  the  body  through  the  skin, 
lungs,  and  kidneys. 

25.  Salts. — The  most  essential  food  of  this  class  is 
common  table  salt.  Meats,  vegetables,  and  fruits  all 
contain  salt,  but  not  enough  to  supply  our  need.  We 
add  salt  tp  nearly  everything  we  eat.  Salt  may  neither 


22  HUMAN   PHYSIOLOGY  CHAP. 

build  tissue  nor  furnish  heat,  and  yet  we  must  eat  con- 
siderable of  it  to  keep  our  bodies  in  good  health.  Each 
cell  must  have  in  it  a  certain  amount  of  common  salt  to 
do  its  work  properly.  Just  what  it  does  we  do  not  know 
with  certainty,  but  it  seems  to  stimulate  the  cells  to 
greater  activity.  It  has  been  estimated  that  the  total 
amount  of  salt  in  the  body  is  less  than  one  half  pound. 

26.  Oxygen.  —  Did    you    ever   think   of   the   air   we 
breathe  as  being  a  food  ?     Many  do  not  call  it  a  food, 
but  we  shall  consider  it  in  connection  with  foods.     We 
know  that  oxygen  breathed  into  the  lungs  gets  into  the 
blood  and  is  then  carried  to  all  the  cells  of  the  body  by 
the  red  corpuscles.     Does  a  fire  burn  well  if  you  close 
the  drafts  that  furnish  it  air?     Well,  the  foods  cannot 
be  oxidized  in  the  cells  without  an  abundant  supply  of 
oxygen.     When  solid  foods,  water,  and  oxygen  are  car- 
ried to  the  cells,  they  undergo  certain  chemical  changes 
there,  i.e.  they  are  slowly  burned  or  oxidized.     This  oxi- 
dation produces  heat  that  is  used  to  keep  up  the  body 
temperature,   and  energy  that   is   used  in   doing  work. 
Oxygen  is  also  used  to  transform  the  foods  we  eat  into 
tissues  of  the  body.     Oxygen  is  so  important  that  we 
could  live  only  a  few  minutes  without  it. 

Put  a  lighted  candle  into  an  empty  fruit  jar.  The  candle-  burns 
brightly  for  a  few  moments,  but  as  soon  as  the  oxygen  in  the  jar  is 
used  up  the  flame  dies.  If  the  candle  is  taken  out,  lighted,  and 
lowered  into  the  jar  again,  it  will  be  extinguished  at  once  because 
there  is  no  oxygen  left  in  the  jar. 

27.  Substances  taken  with  Foods.  —  There  are  many 
things    eaten    simply   because    an    appetite   has   been 


Ill 


FOODS 


formed  for  them.  They  are  then  said  to  be  palatable. 
Mustard,  ginger,  pepper,  pickles,  olives,  vinegar,  horse- 
radish, and  flavors  of  all  kinds  belong  to  this  class. 
Some  of  these  things  have  no  value  whatever  as  foods, 
but  may  be  of  use  to  stimulate  the  appetite  and  to  aid 
digestion  under  certain  conditions,  if  used  moderately. 
When  a  person  is  well  he  seldom  needs  anything  to  stim- 
ulate his  appetite,  and  the  excessive  use  of  all  such  sub- 
stances is  not  only  unnecessary  but  may  be  very  harmful. 
28.  Animal  Foods.  —  The  foods  that  come  from  ani- 
mals are  among  the  most  important  articles  of  our 
daily  meals.  Only  a  few  will  be  mentioned  here. 


FIG.  7.  —  Showing  fat  globules  (Gunnison)  :  A,  cream  ;  B,  milk  ;   and 
C,  skim  milk. 

I.  Milk  is  almost  an  ideal  food.  It  contains  all  the 
food  stuffs  necessary  for  man  and  is  about  the  only 
nourishment  adapted  to  infants.  For  an  adult  the  pro- 
portion of  the  different  food  stuffs  in  milk  is  not  quite 
right.  He  would  be  obliged  to  drink  a  large  quantity 
of  milk  in  order  to  get  the  amount  of  proteids  and 
carbohydrates  necessary.  And,  furthermore,  man  needs 
a  food  that  gives  the  stomach  more  to  do. 


24  HUMAN  PHYSIOLOGY  CHAP. 

2.  Cheese  is  a  valuable  food,  but   cannot    be   easily 
changed  into  blood.     It  should  be  eaten  in  small  quanti- 
ties only. 

3.  Meats  form  a  most  valuable  article  of  diet.     They 
are  the  most  easily  digested  of  all  the  proteids  if  eaten 
in  small  quantities,  and  are  very  nutritious.     There  is 
danger  of  eating  more  meat  than  is  necessary  to  supply 
the  blood  with  tissue-building  foods.     Beef,  fish,  mut- 
ton, lamb,  veal,  pork,  poultry,  and  game  are  among  the 
most  common  meats. 

4.  Eggs  contain  all  the  important  food  stuffs  except 
carbohydrate,   and    may   be    eaten    in    place   of    meats 
occasionally.     They  are  easily  digested,  if  properly  pre- 
pared, and  are  very  nutritious. 

5.  Butter  is  the  fat  of  milk,  and  forms  a  digestible 
and  very  palatable  food.     Bread  and    butter   form    an 
excellent  food. 

29.  Vegetable  Foods.  —  From  the  plant  world  we  get 
a  great  variety  of  articles  of  diet,  many  of  which  are 
very  valuable. 

i.  The  cereals  supply  us  with  bread,  rice,  and  the 
many  breakfast  foods  so  commonly  used  at  present. 
Wheat  bread  is  probably  the  most  widely  used  as  well 
as  the  most  important  of  this  class,  as  it  contains  all  of 
the  food  stuffs  except  fat.  Some  one  has  called  bread 
"the  staff  of  life,"  and  when  butter  is  added  they  to- 
gether form  "the  gold-headed  cane."  Rice,  you  know, 
is  the  food  most  used  in  China.  With  proteids  and  fats 
it  would  give  nearly  as  much  nourishment  as  bread  and 
butter.  Malt,  barley,  wheat,  and  other  cereals,  prepared 


Ill 


FOODS 


in  various  ways  as  breakfast  foods,  are  all  easily  digested 
and  are  very  nutritious  for  most  people. 

2.  The  so-called  vegetables  are  not  very  nutritious, 
but  they  are  cheap  and  easily  digested  and  therefore  are 
used  extensively.  Under  this  head  we  have  the  Irish 
potatoes,  sweet  potatoes,  beets,  carrots,  squash,  cabbage, 
tomatoes,  peas,  beans,  and  lentils.  The  Irish  potato  is 


Prote/ef 
Ash 


Cabbage, 


Potato. 


Carrot. 


FIG.  8.  —  Showing  composition  of  potato,  carrot,  and  cabbage.     Modified  from 
Snyder's  "  Losses  in  boiling  vegetables"  (Zinns). 

the  king  of  vegetables.  Some  of  these  articles,  as  cab- 
bage and  beans,  are  not  easily  digested,  and  some  con- 
tain but  little  nourishment.  Green  vegetables  are  taken 
with  other  foods  because  of  their  palatable  qualities  ; 
they  contain  salts,  acids,  and  aromatic  substances. 

3.  Under  this  class  of  foods  must  be  mentioned  ripe 
fruits,  as  berries,  apples,  oranges,  bananas,  grapes,  etc. 
Most  of  the  fruits  are  valuable  for  their  juices,  which 


26 


HUMAN  PHYSIOLOGY 


CHAP. 


contain  salts,  acids,  and  sugar.  They  are  not  especially 
nourishing. 

4.  Nuts  contain  a  large  amount  of  proteid  and  fat, 
which  makes  them  valuable  as  articles  of  diet.  They 
must  be  well  chewed  and  eaten  in  small  quantities,  for 
they  are  rather  difficult  to  digest.  The  Germans  say 
that  nuts  and  cheese  are  "gold  in  the  morning,  silver 
at  noon,  and  lead  at  night." 

30.  Hygiene.  —  The  foods  we  eat,  the  water  we  drink, 
and  the  air  we  breathe  require  careful  attention,  as  we 
shall  learn  later.  Places  where  foods  are  kept  should 
be  clean  and  well  ventilated.  How  often  are  the  pantry, 
the  ice  box,  and  the  cellar  sadly  neglected!  Air,  water, 
milk,  and  meats  that  are  impure,  and  fruits  artificially 
ripened  or  overripe,  are  often  the  causes  of  diseases. 
We  cannot  be  too  careful  as  to  the  conditions  of  the 
foods  we  take  into  our  systems. 


FIG.  9. —  Trichinae  (Buchholz)  :    A,  trichinae,  as  seen  in  a  muscle  of  a  young 
man  who  died  of  trichinosis ;  B,  a  single  trichina  magnified. 

31.  Value  of  Cooking. — -Why  do  we  cook  foods?  Some 
will  say  because  they  taste  better  and  look  more  at- 
tractive when  cooked.  That  is  true ;  but  there  are  other 


Ill 


FOODS 


27 


reasons  more  important.  In  beef  and  pork  are  some- 
times found  little  parasites  and  germs  that  cause  disease 
if  taken  into  the  body.  Cooking,  if  well  done,  kills  all 
injurious  things  of  this  kind.  We  should  never  eat 
raw  meats.  Many  foods,  especially  vegetables  and 
green  fruits,  are  more  easily  digested  when  cooked. 


Raw 


Partially  cooked. 


Thoroughly  cooked. 


FiG.    10.  —  Showing  how  cooking  changes  the  starch  cells  of  potato.     Drawn 
from  Year-book  of  Department  of  Agriculture,  1900  (Zinns). 

Cooking  causes  the  cell  walls  of  vegetables  to  burst,  and 
so  permits  the  starches  and  sugars  to  escape.  In  meats 
the  connective  tissue  is  loosened,  and  so  the  most  im- 
portant elements  become  exposed  to  the  action  of  the 
juices  in  the  stomach  and  intestines. 

Apply  the  starch  test  to  raw  and  to  boiled  starch.  Do  you  notice 
any  difference  ? 

32.  Amount  of  Food.  —  The  amount  one  should  eat 
depends  upon  age,  health,  occupation,  and  many  other 
things.  On  an  average  an  adult  who  works  moder- 
ately needs  each  day  about  one  fourth  of  a  pound  of 
proteid ;  a  little  less  than  one  fourth  of  a  pound  of  fat ; 
a  little  more  than  three  fourths  of  a  pound  of  carbohy- 


28  HUMAN   PHYSIOLOGY  CHAP. 

drate ;  about  one  eighth  of  a  pound  of  salt ;  and  from 
three  to  five  pounds  of  water.  The  foods  we  eat  each 
day  should  be  so  selected  as  to  yield  this  amount  of 
each  food  stuff  if  we  wish  to  be  in  good  health. 

SUMMARY  OF  THE   MAIN   POINTS 

i.  A  food  is  any  substance  that  enters  the  blood,  and  with- 
out doing  any  harm  in  the  body  helps  to  cause  growth,  to  re- 
pair the  cells,  and  to  yield  heat  and  energy. 

•2.  The  food  stuffs  are  proteids,  carbohydrates,  fats,  salts, 
water,  and  oxygen.  These  food  stuffs  are  oxidized  in  the  cells 
of  the  body. 

3.  Proteids    are    the   tissue-building    and    tissue-repairing 
foods.     They  are  essential  to  life. 

4.  The  carbohydrates  form  the  great  bulk  of  our  daily  diet. 
They  serve  to  yield  heat  and  energy. 

5.  The  fats  are  the  greatest  heat  producers,  but  are  not  as 
valuable  as  the  carbohydrates,  because  they  are  more  difficult 
to  digest. 

6.  Water  is  found  in  all  of  the  foods  we  eat,  but  that  does 
not  meet  the  demand  of  the  body.     We  must  drink  considera- 
ble water  each  day,  for  it  has  many  uses  in  the  body. 

7.  Water  dissolves  the  solid  foods,  moistens  the  mouth  and 
other  organs  to  aid  in  swallowing,  makes  up  a  large  part  of  the 
blood  and  lymph,  and  is  an  essential  part  of  each  cell. 

8.  The  cells  cannot  do  their  work  properly  unless  consid- 
erable salt  is  present. 

9.  Foods  are  of  no  use  to  the  body  without  oxygen;  but 
when  foods  and  oxygen  are  brought  together  in  the  cells,  heat  is 
produced  and  tissues  may  be  built  up  and  repaired. 

10.  Mustard,  ginger,  pepper,  pickles,  olives,  vinegar,  horse- 
radish, and  all  flavors  are  not  true  foods,  and  when  taken  in 
excess  prove  harmful. 


in  FOODS  29 

11.  The   most   important   animal  foods   are    milk,  cheese, 
meats,  eggs,  and  butter. 

12.  Cereals,  vegetables,  fruits,  and  nuts  are  the  important 
foods  obtained  from  the  plant  world. 

13.  All  foods  and  places  where  foods  are  stored  must  be 
clean  and  well  ventilated,  so  that  the  foods  may  be  kept  pure 
and  wholesome. 

14.  Cooking   kills  disease  germs;    makes  foods  attractive 
and  palatable ;  and  in  most  cases  aids  digestion. 

15.  An  adult  who  does  a  moderate  amount  of  work  requires 
every  day  about  one  fourth  of  a  pound  of  proteid ;  one  fourth 
of  a  pound  of  fat ;  three  fourths  of  a  pound  of  carbohydrate ; 
two  ounces  of  salt ;  and  from  three  to  five  pounds  of  water. 


CHAPTER    IV 

DRINKS    AND    NARCOTICS 

33.  Pure  Water.  —  The  clear  and  sparkling  water  of 
our  springs,  wells,  and  lakes,  that  tastes  so  good  and 
forms  really  the  only  drink  necessary  for  man  and 
beast  alike,  is  by  no  means  pure  to  the  chemist. 
Water  that  is  chemically  pure,  —  distilled  water, — is  not 
found  in  nature,  neither  is  it  pleasant  to  drink,  for  it  is 
flat  and  tasteless.  What  is  in  the  spring  water  that 
we  thought  was  pure  and  is  so  agreeable  to  the  taste  ? 
When  it  is  carefully  examined  by  a  chemist,  it  is  found 
to  contain  minerals  of  various  kinds,  and  air.  The 
most  common  minerals  are  lime,  soda,  potash,  iron, 
magnesia,  and  sulphur. 

The  water  that  is  most  healthful  is  not  absolutely 
pure  but  contains  air  and  many  mineral  substances 
that  are  valuable  to  the  body.  It  is  only  when  these 
minerals  are  too  abundant,  and  especially  when  water  con- 
tains disease  germs,  that  it  becomes  dangerous  to  drink. 

1.  Dissolve  salt  or  sugar  in  water  until  you  can  easily  taste  it. 
Then  heat  the  solution  to  the  boiling  point  and  collect  the  vapor 
that  is  given  off.     Do  you  detect  any  taste  ?     What  has  become  of 
the  salt  or  sugar  ? 

2.  Evaporate  the  entire  solution.     Do  you  have  any  solid  left  ? 

30 


CHAP,  iv  DRINKS  AND   NARCOTICS  31 

34.  Impure  Water.  —  Typhoid  fever,  dysentery,  chol- 
era, and  many  other  dangerous  diseases  are  generally 
due  to  germs  that  live  in  the  water.  Many  of  these 
diseases  can  be  traced  directly  to  some  well  located  in 
a  barnyard,  or  other  filthy  place,  from  which  surface 
water  is  drained  into  it.  People  are  often  careless  >* 
in  choosing  a  location  for  a  well  for  drinking  Vrp 
purposes.  It  should  not  be  dug  in  a  low 


FlG.  ii.  — Showing  how  surface  drainage  may  contaminate  the  water  of  a 
badly  located  well  (Zuppke). 

place,  where  water  from  all  directions  may  run  into  it, 
but  on  a  spot  on  a  level  with  the  house  and  barn  and 
sufficiently  removed  from  all  sources  of  contamination. 
The  germs  in  drinking  water  are  the  direct  cause  of 
thousands  of  deaths  yearly,  both  in  the  country  and  in 
our  large  cities. 

Many  people    filter  the  drinking  water.     This  is  an 


32  HUMAN   PHYSIOLOGY  CHAP. 

excellent  precaution  to  take  when  there  is  reason  to 
suspect  disease  germs.  How  can  it  be  purified  ?  There 
is  but  one  safe  way  to  purify  water  containing  disease 
germs,  and  that  is  to  boil  it.  If  the  temperature  of 
water  is  kept  at  the  boiling  point  for  about  twenty  min- 
utes, all  germs  are  destroyed,  and  when  cooled  it  may 
be  safely  taken  into  the  stomach.  The  common  water 
filters  are  of  value  in  removing  the  coarse  substances, 
and  so  making  the  water  look  clear  and  pure ;  but  they 
cannot  be  relied  upon  to  remove  the  germs  that  cause 
disease  unless  they  are  properly  cared  for. 

In  connection  with  bad  water  we  must  discuss  ice. 
Ice  is  just  as  impure  as  the  water  of  which  it  was 
formed,  because  freezing  does  not  kill  the  disease 
germs.  Ice  from  lakes  or  rivers  whose  waters  are 
unfit  for  drinking  purposes  should  not  be  put  into 
drinking  water  nor  used  in  ice  boxes  in  which  foods  are 
kept.  Serious  diseases  are  often  traced  to  the  use  of 
impure  ice.  The  excessive  use  of  ice  water  is  an 
American  habit  that  cannot  be  defended  from  the 
standpoint  of  health.  The  temperature  of  substances 
taken  into  the  stomach  should  not  be  below  44°  F.  nor 
above  131°  F. 

35.  Tea  and  Coffee.  —  These  are  not  foods,  but  have 
become  almost  universal  beverages  with  meals,  in  place 
of  water.  Both  contain  substances  that  have  a  stimu- 
lating effect  upon  the  muscles  and  the  nerves.  Some 
people  use  tea  or  coffee  when  very  tired  because 
they  make  them  feel  better.  This  is  because  they  re- 
store muscular  activity  and  stimulate  the  brain  cells. 


IV  DRINKS   AND  NARCOTICS  33 

Tea  and  coffee  excite  the  nerves,  so  that  one  does  not 
realize  that  he  is  tired. 

Some  adults  who  are  well  and  strong  may  use  these 
drinks  without  feeling  any  harm  whatever,  unless  they 
are  taken  in  too  large  quantities  or  are  made  too  strong. 
Persons  who  are  weak,  however,  may  find  that  even 
a  cup  of  tea  or  coffee  taken  daily  causes  serious 
nervous  disturbances,  including  sleeplessness  and  rest- 
lessness, as  well  as  disorder  to  digestion.  Children 
should  not  use  either  tea  or  coffee,  because  they  retard 
physical  growth,  make  the  complexion  dark  and  muddy, 
stimulate  the  kidneys  too  much,  delay  digestion,  and 
have  a  harmful  effect  upon  their  delicate  and  sensitive 
nervous  systems.  The  use  of  tea  frequently  causes 
muscular  tremor. 

The  extensive  use  of  tea  and  coffee  is  simply  a 
matter  of  habit.  A  person  in  good  health  does  not 
need  these  stimulants,  and  their  excessive  use  is  the 
cause  of  much  of  the  nervousness  and  poor  digestion 
so  common  in  this  country.  We  should  drink  only 
those  things  that  will  keep  us  strong  and  well. 

6.  Milk.  —  We  have  learned  that  milk  is  almost  an 
ideal  food,  and  as  a  beverage  it  should  rank  next  to 
water  in  importance.  It  does  not  agree  with  some,  but 
most  persons  find  it  a  very  satisfactory  substitute  for 
tea  and  coffee.  Great  care  must  be  taken  to  keep  the 
milk  free  from  disease  germs,  because  it  easily  absorbs 
any  impurities  the  air  may  contain.  In  the  cellar  or 
ice  box  no  vegetables,  cheese,  or  meats  should  be  kept 
with  milk  if  it  is  not  in  sealed  bottles.  If  strong 


34  HUMAN   PHYSIOLOGY  CHAP. 

cheese,  or  a  bunch  of  onions,  and  milk  are  placed  side 
by  side,  the  latter  will  soon  be  tainted  with  the  odor  of 
the  former.  Vessels  containing  milk  should  always  be 
covered,  or,  still  better,  sealed. 

Milk  of  diseased  cows  or  that  which  has  not  been 
kept  clean  is  dangerous  to  use.  Typhoid  fever  and 
other  serious  diseases  are  often  due  to  the  use  of  im- 
pure milk.  We  should  use  fresh,  wholesome  milk  more 
and  more  with  our  meals  instead  of  tea  and  coffee  and 
other  less  valuable  beverages,  for  it  is  an  excellent 
drink  and  at  the  same  time  a  very  nutritious  food. 

Place  some  milk  in  a  shallow  pan,  in  an  ice  box,  side  by  side  with 
onions,  cheese,  or  vegetables,  and  notice  that  the  milk  becomes 
tainted  in  a  short  time. 

37.  Alcohol.  —  If  sweet  apple  juice  be  allowed  to 
stand  for  some  time  in  a  warm  place,  it  slowly  loses  its 
sweetness  and  finally  becomes  strong  and  biting  to  the 
taste.  What  has  happened  ?  The  sugar  of  the  apple 
juice  has  been  changed  into  a  gas,  called  carbon  dioxid, 
that  you  can  see  bubbling  up 
through  the  liquid  and  escaping 
into  the  air,  and  into  alcohol 
which  remains  in  the  liquid  and 
gives  it  its  strong  biting  taste. 

What  makes  the   sugar  break 
up   into  carbon  dioxid  and  alco- 

FIG.  12.- Yeast  plants  hol  p      There  js  a  tiny  yeast  plant 

(Buchholz). 

on  all  fruits  and  in  the  air.    When 

the  apples  were  crushed  this  plant  was  in  the  liquid  and 
began  to  live  on  the  sugar  as  its  food.  The  yeast  plant 


iv  DRINKS  AND   NARCOTICS  35 

multiplies  very  rapidly.  In  a  short  time  these  myriads 
of  plants,  called  ferments,  change  all  the  sugar  into 
alcohol  and  carbon  dioxid. 

All  alcohol  is  manufactured  by  yeast  plants  living  and 
growing  in  the  sugar  of  fruits  and  vegetables.  We  call 
this  change,  due  to  the  yeast  plant,  fermentation,  and  the 
liquid  formed,  fermented  liquor.  Since  many  ways  of 
obtaining  alcohol  have  been  devised  there  are  numerous 
varieties  of  alcoholic  beverages.  But  whatever  its  source 
it  has  the  same  effect  upon  plants,  animals,  and  man. 

Put  one  part  of  molasses  to  ten  parts  of  water,  and  a  few  crumbs 
of  yeast  into  a  fruit  jar  or  large  bottle,  and  shake  the  mixture 
thoroughly.  Cover  it  with  a  saucer  and  set  it  away  in  a  warm  place 
for  a  day.  Do  you  notice  bubbles  rising  in  the  liquid  ?  These 
are  carbon  dioxid.  Test  the  gas  above  the  liquid  with  a  burning 
match,  and  with  lime  water.  The  sugar  has  been  decomposed  into 
carbon  dioxid  and  alcohol  by  the  growing  yeast  plant.  If  it  is  left 
to  continue  for  several  days,  the  alcohol  will  be  broken  up  into  vine- 
gar and  water.  What  happens  when  preserves  "work,"  or  when 
cider  becomes  hard  ?  Why  is  yeast  used  in  making  bread  ?  Why 
is  bread  sometimes  sour  ?  Why  soggy  ? 

38.  Alcoholic  Drinks. — The  following  are  among  the 
most  common  beverages  which  contain  alcohol :  wines, 
beers,  and  spirits. 

1.  Wines  are  made  from  the  juice  of  the  grape  and 
various  small  fruits,  as  the  currant,  blackberry,  elder- 
berry, raspberry,  cherry,  gooseberry,  etc.     The  percent- 
age  of   alcohol  in  wine    depends  upon  the  amount  of 
sugar   in   the   fruit   from    which   the   wine   was  made. 
Wines  contain  from  six  to  twenty  per  cent  of  alcohol. 

2.  Quite  like  the  wines  are  apple,  pear,  and  orange 
cider. 


36  HUMAN   PHYSIOLOGY  CHAP. 

3.  Malt  beverages,  as  beer,  porter,  and  ale,  are  made 
from  barley,  wheat,  corn,  and  rice.      The  beers  contain 
less  alcohol  than  the  wines,  the  amount  varying  from 
two  to  eight  per  cent. 

4.  The  home-made  beers,  as  the  root  and  birch,  con- 
tain from  one  to  three  per  cent  of  alcohol. 

5.  Spirits  or  distilled  liquors  are  all  produced  by  a 
process  of  distillation  and  contain  a  high  percentage  of 
alcohol.      Whisky,  which  contains  from  thirty  to  sixty 
per  cent  of  alcohol,  is  made  from  rye,  corn,  potatoes,  and 
other   things   rich   in    starch.      Brandy   contains   from 
fifty  to  sixty  per  cent  of  alcohol  and  is  made  chiefly  from 
wines  of  various   kinds.     Rum    contains  from  sixty  to 
seventy  per  cent  of  alcohol  and  is  made  from  cane  sugar 
and  molasses.     The  alcohol  formed  by  fermentation  has 
essence    of   rum  added  to  it.     Gin   is    produced   from 
wines  and  whiskies  by  double  distillation  and  is  flavored 
with  juniper  berries,  coriander,  almond  cake,  or  various 
other  aromatic  substances. 

39.  Is  Alcohol  a  Food  ? — Alcohol  is  not  a  food  but  a 
poison.  We  all  know  the  poisonous  effect  alcohol  pro- 
duces upon  the  young,  even  when  taken  in  small  quan- 
tities ;  and  in  large  amounts  it  acts  like  a  narcotic  poison 
that  paralyzes  the  nervous  system  and  has  been  known 
to  destroy  life.  You  will  remember  that  our  definition 
of  foods  says,  "and  without  doing  any  harm  in  the 
body,"  which  at  once  bars  out  all  alcoholic  drinks.  It 
is  claimed  that  alcohol  may  be  oxidized  in  the  body,  like 
carbohydrates  and  fats,  and  produce  heat  to  keep  us 
warm.  While  this  may  be  true  as  is  shown  by  many 


iv  DRINKS  AND   NARCOTICS  37 

careful  experiments,  yet  because  of  its  harmful  effects 
it  cannot  be  classed  with  those  things  that  go  to  make 
muscle  and  brain,  to  give  us  strength,  to  keep  us  warm, 
and  to  make  us  useful,  happy,  healthy  individuals. 

40.  The   Appetite  for   Alcohol.  —  If  any  of  the  bev- 
erages containing  alcohol  are  used  occasionally,  even  in 
small  quantities,  the  body  becomes  accustomed  to  them 
and  craves  them  when  they  are  not  regularly  provided. 
More  than  that,  they  create  an  artificial  appetite,  a  crav- 
ing, which  can  be  satisfied  only  by  taking  a  constantly 
increasing   amount.     That   is    not  true  of  food.     Our 
appetite   for   potatoes,  bread,  or  beefsteak   can   be    as 
readily  satisfied  to-day  as  a  year  ago,  and  it  will  not  take 
a  larger  quantity  a  year  hence.     Anything  we  eat  or 
drink  for  which  such  an  artificial  appetite  is  acquired 
must  be  looked  upon  with  great  suspicion.     Total  absti- 
nence is  the  only  real  safeguard  against  the  unnatural 
craving  for  alcohol.     We  shall  learn  in  later  chapters  of 
the  effects  of  alcoholic  drinks  upon  the  various  organs 
of  the  body. 

41.  Tobacco.  —  No  one  claims  that  tobacco  is  a  food 
or  a  necessity  for  our  well-being.      All  regard  it  as  a 
luxury,  and  an  expensive  one  at  that.    Tobacco  contains 
nicotine,  a  violent  narcotic  poison,  to  which  its  harmful 
effects   are   due.     Smoking   and    chewing  are  useless, 
expensive,  and  injurious  habits. 

While  an  adult  may  not  be  aware  of  the  harmful 
effects  due  to  the  constant  use  of  tobacco,  a  young  per- 
son cannot  conceal  the  injuries  to  both  body  and  mind 
that  result  from  its  use.  Physicians  tell  us  that  it 


38  HUMAN   PHYSIOLOGY  CHAP. 

dwarfs  physical  growth  and  development  of  the  young, 
produces  harmful  effects  upon  many  organs  of  the  body, 
as  the  brain,  heart,  and  stomach,  and  acts  in  a  most  inju- 
rious way  upon  the  memory  and  all  other  mental  powers. 
42.  Cigarettes.  —  Cigarettes  contain  the  same  narcotic 
poisons  found  in  tobacco.  The  purest  cigarette  contains 
nicotine.  It  is  said  that  waste  tobacco  and  cigar  stumps 
are  frequently  used  in  the  manufacture  of  the  cheaper 
grades  of  cigarettes.  Of  course  the  amount  of  poison 
in  a  cigarette  must  be  very  small,  and  yet  the  cigarette 
habit  so  common  among  boys  and  young  men  is  more 
harmful  to  health  and  vigorous  mental  activity  than  the 
use  of  tobacco  in  any  other  form.  This  is  true  because 
the  cigarette  is  so  very  mild  that  the  smoker  gets  little 
satisfaction  unless  some  of  the  smoke  is  inhaled.  In 
this  way  the  smoke  affects  not  only  the  mouth,  throat, 
and  nose,  but  all  the  air  passages  and  even  the  lungs. 
As  the  habit  grows,  more  and  more  of  the  poison  is 
taken  into  the  lungs,  where  it  comes  in  contact  with  the 
blood.  It  is  then  carried  to  all  the  organs  and  tissues 
of  the  body.  It  is  the  way  in  which  the  cigarettes  are 
used  that  makes  them  so  dangerous  to  the  young.  A 
young  man  who  wishes  to  keep  his  body  well  and  strong 
cannot  afford  to  get  into  the  habit  of  using  narcotic 
poisons  in  any  form. 

SUMMARY   OF  THE   MAIN   POINTS 

i.  Absolutely  pure  water  is  tasteless,  but  when  it  contains 
only  mineral  salts  or  other  things  that  are  not  injurious  it  is 
the  most  palatable  and  healthful  drink  we  have. 


V  DRINKS   AND   NARCOTICS  3$ 

2.  Impure  water  is  very  dangerous,  for  it  may  contain  germs 
that  cause  the  most  dreaded  diseases  known  to  man,  as  cholera, 
typhoid  fever,  etc. 

3.  Boiling  is  the  only  safe  way  to  purify  water,  because  no 
other  means  can  remove  or  destroy  the  disease  germs.     Filters 
have  some  value. 

4.  The  ice  that  forms  on  stagnant  ponds,  lakes,  and  rivers, 
whose  waters  are  unfit  to  drink,  should  not  be  used  for  drinking 
purposes,  because  it  is  just  as  impure  as  the  water  upon  which 
it  forms.     Freezing  does  not  kill  disease  germs. 

5.  Next  to  water,  milk  is  the  most  wholesome  drink,  and  it 
will  be  used  more  generally  as  we  learn  more  of  its  value.     Im- 
pure milk,  however,  is  very  dangerous. 

6.  Tea  and  coffee  contain  poisons  that  act  as  stimulants 
upon  the  nerves,  and  a  young  person  in  good  health  does  not 
need  to  use  either.     We  are  better  off  if  we  let  them  alone. 

7.  The  yeast  plant  feeds  upon  the  sugar  of  vegetables  and 
fruits  and  slowly  breaks  it  up  into  carbon  dioxid  and  alcohol. 
The  carbon  dioxid  is  a  gas  and  escapes,  but  the  alcohol  re- 
mains in  the  liquid  and  gives  it  a  strong  biting  taste.     Yeast 
and  other  things  that  act  in  the  same  way  are  called  ferments. 

8.  Wines,  beers,  and  spirits  are  the  common  varieties  of 
beverages  that  contain  alcohol. 

9.  Alcohol  produces  harmful   effects  upon  the  body  of  a 
growing  boy  or  girl  and  therefore  cannot   be    classed  among 
foods  or  wholesome  drinks. 

10.  The  youth  who  takes  alcohol  in  any  form  finds  that  he 
needs  a  constantly  increasing  quantity  to  satisfy  his  abnormal 
appetite. 

1 1 .  Nicotine  of  tobacco  has  a  harmful  effect  upon  the  brain, 
heart,  stomach,  and  other  organs  of  the  body.     Its  effect    is 
most  marked  upon  the  young. 


CHAPTER  V 

RESPIRATION 

43.  Review.  —  We  have   learned   what  the  cells   of 
the  human  body  consist  of,  and  what  they  need  in  order 
to  do  their  work  well  and  to  keep  us  in  good  health.     We 
have  learned  which  foods  are  most  nutritious  and  what 
substances  are  harmful.     We  have  also  learned  what 
we  should  drink  to  keep  in  perfect  health.     The  foods 
we  eat  and  the  liquids  we  drink  can  be  used  by  the  cells 
of  the  body  only  when  there  is  a  large  amount  of  fresh 
air  (oxygen)  in  the  cells.     The  oxygen  of  the  air  com- 
bines with  the  foods,  causing  a  very  slow  burning  or 
oxidation  to  take  place  in  the  cells. 

We  must  now  learn  how  the  air  gets  from  the  room 
in  which  we  live  into  each  and  every  cell  of  the  body, 
where  it  is  used.  That  whole  process  we  call  respi- 
ration. 

44.  The   Air   Passages.  —  We   breathe   through   the 
skin  as  some  of  the  lower  animals  do,  but  most  of  the 
air  gets  into  the  blood  through  a  number  of  tubes  that 
together  are  called  the  air  passages.     Air   enters    the 
body  through  the  nose,  which  is  the  beginning  of  these 
air  tubes.     Then    follow  the    pharynx,  larynx,  trachea 
(windpipe),  two   bronchi,   many  bronchial    tubes,    and, 

40 


CHAP.  V 


RESPIRATION 


finally,  thousands  of  little  air  pouches,  or  sacs  of  the 
lungs. 

These  tubes  are  made  of  a  firm  substance  like  gristle, 
called  cartilage,  which  gives  them  their  shape  and  holds 
them  open  so  that  we  can 
breathe  easily  day  and 
night.  The  cartilage  is 
covered  with  muscles  and 
connective  tissue.  The 
tubes  are  all  lined  with 
a  moist,  delicate,  velvety 
lining  called  a  mucotis 
membrane.  The  differ- 
ent organs  of  the  air 
passages  are  alike  in 
their  general  structure, 
but  they  differ  much  in 
size  and  shape. 

45.  The  Nose. —This 
diagram  shows  how  large 
and  irregular  is  the  space 
in  the  nose  through 
which  air  passes.  That 
is  for  the  purpose  of 


FIG.  13.  —  Showing  the  nose  and  mouth. 
(From  Huxley's  "  Elementary  Physi- 
ology ")  :  a,  spinal  column ;  b,  food 
passage  or  gullet ;  c,  windpipe  ;  d,  voice 
box;  e,  epiglottis;  /  soft  palate; 
g,  Eustachian  tube ;  h,  opening  of  the 
tear  duct;  i,  hyoid  bone;  k,  tongue; 
/,  hard  palate ;  m,  n,  bones  of  the  skull ; 
o,  p,  q,  turbinate  bones  of  the  nose. 


spreading    the    air    out 

over  a  large  area,  so  that 

it  may  be  changed  to  the 

temperature  of  the  body 

before  going  into  the  delicate  little  air  sacs  of  the  lungs. 

The  moist  mucous  membrane  of  the  nose  picks  out  dust 


HUMAN   PHYSIOLOGY 


CHAP. 


FIG.  14.  — Cili- 
ated cells 
from  the  nose 
(Zinns) . 


fp/g/ott/s 


and  foreign  substances  by  means  of  its 
hairs  and  hairlike  cilia.  Besides  doing 
all  this,  the  nose  is  the  organ  of  smell. 
Little  nerve  endings  are  found  in  the 
mucous  membrane  of  the  upper  part  of 
the  nose,  that  enable  us  to  smell. 

Why  should  we  breathe  through  the 
nose  rather  than  through  the  mouth  ? 
The  nose  warms,  moistens,  and  purifies 

the  air  and  is  the  natural  channelmade  for  breathing. 

If  persons  breathe  through  the  mouth,  they  cannot  de- 
tect foul  air  by  its  odor ;  the  mucous  membrane  of  the 

mouth   and  throat  become  dry ;    cold,  dry  air  reaches 

the  delicate  tissues  of  the 

lungs,  where  it  is  sure  to 

cause  discomfort  and  even 

disease ;    and   all  the   fine 

particles  of  dust  and  dirt 

floating    about    in   the    air 

pass  down  into  the  lungs. 

We  should  always  breathe 

through  the  nose. 

46.     The    Pharynx    and 

Larynx.  —  After    passing 

through    the    two    nostrils 

the  air  enters  the  pharynx. 

This  is  a  rather  large  fun- 
nel -  shaped      organ      that 

serves  as  a  reception  hall 

for  both  air  and  foods.    At         FIG.  15.—  Larynx  (Zuppke). 


RESPIRATION 


43 


the  lower  part  of  the  pharynx*  the  air  leaves  it  and 
enters  the  larynx  through  an  opening  called  the  glottis. 
The  top  of  the  larynx  is  guarded  by  a  trapdoor  (epi- 
glottis) which  closes  the  glottis  in  the  act  of  swallowing, 
and  so  prevents  food  and  drink  from  entering  the  air 
tubes  leading  to  the  lungs. 


FIG.  16. —  Larynx,  trachea,  and  bronchi.      From  Heitzmann's  "Anatomy" 
(Becker). 

The  larynx  (voice  box)  is  a  very  delicately  constructed 
organ,  serving  both  as  a  passage  for  air  and  as  the 
organ  for  producing  voice.  It  is  a  very  useful  organ 
and  will  be  described  more  fully  in  a  later  chapter. 

47.  The  Trachea  and  Bronchial  Tubes.  —  The  larynx 
ends  below  in  the  trachea,  or  windpipe,  which  is  a  tube 


44  HUMAN  PHYSIOLOGY  CHAP. 

about  four  and  one  half  inches  long  and  three  fourths  of 
an  inch  in  diameter.  The  cartilages  of  the  trachea  are 
in  the  form  of  small  C-shaped  rings  held  in  place  by 
muscles  and  connective  tissue.  The  trachea  divides  at 
its  lower  extremity  into  two  smaller  air  passages,  called 
the  right  and  left  bronchi,  going  to  the  two  lungs.  Each 

of  these  gives  rise  to 
many  still  smaller 
passages,  called  bron- 
chial tubes,  which  get 
lighter  and  finer  until 
they  end  in  the  air 
sacs.  The  cartilage 

FiG.  17.  —  Showing  how  a  bronchiole  ends  in     has  gradually  become 
air  sacs.     (After  Schafer.)  ,  .  ^. 

thinner,     the      rings 

have  disappeared,  the  muscle  fibers  have  slowly  faded 
out,  and  even  the  delicate  mucous  membrane  has  be- 
come so  thin  that  air  can  easily  pass  through  it  into  the 
small  blood  vessels  of  the  lungs. 

Thus  we  see  the  course  through  which  the  air  is  led 
from  the  atmosphere  into  the  blood  vessels  of  the  lungs. 
How  it  gets  to  the  tissues  we  shall  study  later. 

Get  a  windpipe  from  the  meat  market. 

1.  Cut  out  one  of  the  rings  of  cartilage  and  clean  off  all  the 
muscle  and  connective  tissue.     Compare  the  cartilage  with  bone. 

2.  Cut  off  a  portion  of  the  lining,  which  can  easily  be  seen  when 
the  windpipe  is  cut  open.     It  consists  of  mucous  membrane. 

48.  The  Lungs. — The  lungs  are  two  large,  pinkish, 
spongy  masses  that  completely  fill  the  chest  (thorax), 
except  that  part  which  the  heart  occupies.  The  chest 


v  -   RESPIRATION  45 

is  bounded  below  by  the  diaphragm,  a  large  dome- 
shaped  muscle  that  divides  the  body  into  two  parts, 
called  the  chest  and  the  abdomen,  and  above  by  the 
muscles  of  the  neck. 

The  healthy  lungs  of  a  young  person  have  a  pale 
pinkish  color,  while  the  lungs  of  an  old  man  who  has 
lived  many  years  in  a  city  full  of  dust  and  smoke  have 
a  dark  brown,  almost  black,  color. 


FIG.  18.  —  Front  view  of  the  lungs,  heart,  and  large  blood  vessels  (Zuppke). 

The  right  lung  is  a  trifle  larger  than  the  left,  weighing 
about  two  ounces  more.  Each  lung  is  composed  of 
parts  or  divisions  called  lobes.  The  right  has  three 
lobes  and  the  left  two.  The  lobes  in  turn  are  made  up 
of  numerous  small  lobules.  Did  you  ever  notice  the 
peculiar  mottled  appearance  of  a  fresh  lung  ?  Each 
of  the  little  areas  is  a  lobule.  If  we  look  at  a  lobule 
under  the  microscope,  we  shall  see  that  it  consists  of 
bunches  of  sacs  rilled  with  air  and  capillaries  filled  with 


46  HUMAN   PHYSIOLOGY  .CHAP. 

blood.      It   is  in  these  small  lobules  that   the  air  we 
breathe  comes  in  contact  with  the  blood. 

1.  Procure  a  sheep's  lungs  and  notice  the  size,  shape,  color,  and 
texture.     Notice  the  air  tubes  leading  to  each  lung.     Will  the  lungs 
float  in  water  ? 

2.  Blow  up  the  lungs  by  breathing  into  the  windpipe. 


FIG.  19.  —  Showing  the  trachea,  right  lung,  and  the  bronchial  tubes  of  the  left 
lung  (Zuppke). 

49.  Covering  of  the  Lungs.  —  Each  lung  is  closely 
covered  with  a  thin,  delicate,  saclike  serous  membrane 
called  ihefl/eura.  The  outer  part  of  this  sac  lines  the 
walls  of  the  chest,  while  the  inner  part  covers  the  lungs. 
There  is  a  small  amount  of  fluid  in  the  sacs  which  serves 
to  keep  the  membrane  moist,  and  so  prevents  friction 
and  disease  which  would  result  from  the  constant  rub- 


RESPIRATION 


47 


P/eura 


bing  of  the  surfaces  due  to  the  movement  of  the  lungs 
and  chest  in  breathing.     The  liquid  serves  as    a  natu- 
ral   oil   to    lubricate 
the  membranes  and 
hence      to      make 
breathing  easy. 

50.  How  the  Air 
gets  into  the  Lungs. 
—  We  have  learned 
about  the  passages 
through  which  the 
air  is  conveyed  to 
the  lungs.  But  how 
do  we  breathe  ? 
What  makes  the  air 
go  into  these  pas- 
sages ?  We  shall 
try  to  answer  these 
questions.  We  know  that  the  chest  rises  and  falls  and 
the  ribs  move  in  and  out  in  breathing.  We  cannot  see 
the  diaphragm,  but  that  dome-shaped  partition  moves 
up  and  down  when  we  breathe.  The  chest  enlarges  in 
all  directions,  due  to  the  contraction  of  the  muscles  of 
the  neck  (scalene)  and  the  muscles  of  the  ribs  (inter- 
costal) and  the  diaphragm.  All  these  muscles  work 
together  in  such  a  way  as  to  reenforce  each  other  con- 
stantly. When  these  muscles  contract,  the  chest  en- 
larges, and  the  lungs  also  enlarge  to  fill  the  chest 
completely.  The  amount  of  these  movements  we  can 
easily  measure  with  a  tapeline.  Try  it  and  see  how 


FIG.  20.  —  Showing  how  the  pleurae  cover  the 
lungs  (Zuppke). 


HUMAN   PHYSIOLOGY 


CHAP. 


much  larger  round  your  chest  is  after  you  breathe  in 
(inhale)  than  after  you  breathe  out  (exhale).  Now 
measure  once  more  after  you  have  inhaled  all  you  can 
hold,  and  again  after  you  have  forced  out  all  you  can 
possibly  exhale. 


i 


...10 


u 


FIG.  21.  —  Showing  the  heart  and  lungs  in  position  in  the  thorax.  (From 
Huxley's  "  Elementary  Physiology  "):  1-12,  ribs;  s,  breast  bone ;  c,  c,  car- 
tilages of  ribs ;  c,  collar  bone ;  /,  lungs ;  a,  apex  of  heart ;  peric,  pericar- 
dium, inclosing  the  heart. 

Every  time  the  chest  enlarges,  air  is  pushed  in 
through  the  air  passages  to  keep  the  lungs  full.  When 
the  muscles  relax,  the  chest  grows  smaller,  the  lungs 


RESPIRATION 


49 


are  compressed,  and  air  escapes  freely  through  the' 
air  passages,  and  we  exhale.  We  can  easily  under- 
stand how  we  exhale  because,  when  the  chest  grows 
smaller,  air  is  pushed  out  through  the  air  passages  just 
as  water  may  be  squeezed 
out  of  a  sponge.  But  how 
do  we  inhale  ?  What  pushes 
air  into  the  lungs  through 
the  air  passages  ?  This  is 
not  quite  as  easy  to  under- 
stand. The  atmosphere  is 
exerting  a  pressure  of  about 
fifteen  pounds  on  every 
square  inch  of  surface. 
Since  the  air  in  the  lungs 
and  the  atmosphere  outside 
are  connected  by  means  of 
open  tubes,  the  air  passages,  the  atmospheric  pressure  in 
the  lungs  must  remain  about  fifteen  pounds  to  the  square 
inch.  Now,  when  the  lungs  enlarge,  air  must  be  forced 
into  them  to  keep  the  pressure  the  same  as  it  is  outside. 
We  may  say  that  the  atmospheric  pressure  forces  air 
into  the  lungs  when  the  chest  enlarges,  and  we  inhale. 

This  constant  rhythmic  change  in  the  volume  of  the 
air-tight  chest  makes  inspiration  and  expiration  alter- 
nate all  the  time  from  birth  to  death,  with  no  attention 
whatever  on  our  part.  We  never  need  to  think  about 
breathing,  because  the  nervous  system  is  so  beautifully 
and  perfectly  adjusted  that  it  keeps  up  this  important 
process  with  never  failing  accuracy  and  faithfulness. 


FIG.  22.  —  Showing  positions  of  the 
diaphragm,  sternum,  and  walls  of 
the  abdomen  in  inspiration  and 
expiration  (Zuppke). 


5° 


HUMAN   PHYSIOLOGY 


Coughing,  sighing,  crying,  laughing,  sobbing,  sneez- 
ing,   yawning,    snoring,    singing,    and   talking    are    all 
respiratory  movements  of  a  modi- 
fied nature. 


FIG.  23.  —  Showing  how  the  movement  of  the  diaphragm  changes  the  capacity 
of  the  lungs  (Zuppke) . 

Cut  off  the  bottom  from  a  bottle.  Tie  on  a  piece  of  dentist's 
rubber  for  a  bottom  and  attach  a  small  elastic  bag  to  a  piece  of  glass 
tubing  that  extends  through  a  well-fitting  cork,  as  shown  in  the  figure. 
The  bag  represents  the  lungs ;  the  glass  tubing  the  windpipe ;  the 
bottle  the  chest;  the  dentist's  rubber  the  diaphragm.  When  the 
diaphragm  is  pushed  up,  the  capacity  diminishes  and  the  rubber 
bag  collapses.  Explain.  Compare  with  the  action  of  the  lungs. 

51.  Capacity  of  the  Lungs.  —  It  is  not  possible  to 
determine  accurately  the  capacity  of  the  lungs.  By 
means  of  a  spirometer  it  is  easy  to  measure  the  amount 
of  air  inhaled  and  exhaled  in  ordinary  quiet  breathing. 


v  RESPIRATION  51 

This  is  about  thirty  cubic  inches  and  is  called  the  tidal 
air. 

We  can  also  measure  the  amount  of  air  that  we  can 
force  out  by  the  most  violent  effort  after  an  ordinary 
expiration.  This  is  about  one  hundred  cubic  inches  and 
is  known  as  the  reserve,  or  supplemental  air.  After  an 
ordinary  inspiration  we  can  inhale  about  one  hundred 


FIG.  24.  —  Testing  the  lungs  on  the  spirometer  (Zuppke). 

cubic  inches  more.  This  we  call  the  complemental  air. 
Thus  after  a  forced  inspiration  we  can  exhale  the  com- 
plemental, the  tidal,  and  the  supplemental  air,  amount- 
ing in  all  to  about  two  hundred  and  thirty  cubic  inches. 
This  is  called  the  vital  capacity,  or,  simply,  the  lung 
capacity.  But  after  a  forced  expiration  there  still 
remains  in  the  lungs  about  one  hundred  cubic  inches 
which  cannot  be  expelled  by  any  possible  means.  This 


HUMAN   PHYSIOLOGY 


CHAP. 


Complcmental  Air 
About  120  cu.  in. 


TMalAir 
About  30  cu.  in. 


Supplemental  A  ir 
Ajout  100  cu.  in. 


Residual  Air 
About  100  cu.  in. 


FIG.  25. —  Showing  lung 
capacity. 

ingly  thin-walled,  spherical  pouches. 
On  the  outer  surface  of  these 
thin  sacs  are  very  small,  deli- 
cate blood  capillaries  so  closely 
packed  together  that  they  really 
form  a  little  film  of  blood  cover- 
ing the  whole  outer  surface  of 
the  sacs.  This  film,  if  spread  out, 
would  have  an  area  of  over  fif- 
teen hundred  square  feet.  Large 
surfaces  of  blood  and  air  are 
thus  brought  close  together. 


is  called  the  residual  air.  The 
total  lung  capacity  is  about  tJiree 
hundred  and  thirty  cubic  inches 
for  an.  average  adult. 

The  figure  to  the  left  shows  in 
a  clear  way  the  lung  capacity 
and  will  help  you  to  remember  it. 

52.  How  Air  gets  into  the  Blood. 
—  We  have  just  learned  how  air 
gets  into  the  lungs  and  how  much 
the  lungs  can  hold.  Let  us  now 
see  how  the  air  gets  from  the  lungs 
into  the  blood,  and  how  the  carbon 
dioxid  and  other  wastes  formed 
in  the  cells  of  the  tissues  get  from 
the  blood  into  the  air  sacs  of  the 
lungs.  The  air 
sacs  are  exceed- 


FlG.  26.  —  Showing  the  rela- 
tion of  capillaries  to  air  cells 
in  the  lungs  (Zuppke). 


RESPIRATION 


53 


rjjfcrjT"  —  Copper  sulphate 


FlG.  27.  —  Showing  osmosis  (Zuppke). 


It  is  a  well-known  fact  that  gases,  liquids,  and  even 
solids  that  are  perfectly  dissolved  can  pass  through 
delicate,  living  membranes.  That  is  just  what  happens 
in  the  lungs.  The  oxy- 
gen passes  through  the 
walls  of  the  air  sacs  and 
capillaries  and  enters 
the  blood,  where  it  is 
picked  up  by  the  red 
corpuscles,  which  then 
carry  it  to  the  tissues  all 
over  the  body.  The 
carbon  dioxid  and  other 
wastes  that  are  found  in 
the  blood  enter  the  air  sacs  of  the  lungs  in  a  very 
similar  way  and  are  exhaled.  This  exchange  of  sub- 
stances through  a  membrane  is  called  osmosis. 

1.  Take  a  fresh  hen's  egg  and  remove  the  shell  from  the  larger 
end  so  as  to  expose  the  delicate  membrane  beneath.     Immerse  the 

•egg,  large  end  up,  in  a  glass  of  water  and  set  it  aside  for  a  few  hours. 
The  water  will  slowly  pass  through  the  delicate  membrane,  causing 
it  to  bulge  out.  The  water  soaks  through  the  thin  animal  mem- 
brane just  as  the  gases  do  in  the  air  sacs  of  the  lungs. 

2.  Tie  a  piece  of  bladder  tightly  over  the  bottom  of  a  small  bottle 
from  which  the  bottom  'has  been  removed.     Fill  the  bottle  with  a 
strong  solution  of  copper  sulphate.     Fit  a  cork  with  a  piece  of  glass 
tubing  to  resemble  the  thistle  tube  shown  in  the  figure.     Immerse 
the  bottle  in  a  glass  of  water.     The  next  day  the  water  will  have 
risen  in  the  glass  tube,  and  some  of  the  copper  sulphate  will  be  found 
in   the  glass,  showing  that  there  has  been  an  interchange  of  sub- 
stances through  the  membrane.     An  Argand  lamp  chimney  may  be 
used  instead  of  the  bottle.     Alum,  sugar,  or  common  salt  may  be 
used  instead  of  copper  sulphate. 


54 


HUMAN   PHYSIOLOGY 


CHAP. 


53.  Changes  in  the  Air.  —  The  air  we  inhale  is  a  mix- 
ture of  oxygen,  nitrogen,  carbon  dioxid,  argon,  and  more 
or  less  moisture.  As  it  comes  from  the  lungs  the  same 
things  are  found  in  it,  but  their  proportion  has  been  very 
much  changed,  as  is  shown  by  the  following  table  :  — 


NITROGEN 

OXYGEN 

CARBON 
DIOXID 

ORGANIC 
MATTER 

WATERY 
VAPOR 

Inhaled  air 

79 

21 

.04 

none 

variable 

Exhaled  air 

79 

16 

4.0 

a  little 

saturated 

1.  The  air  has  lost  oxygen.     The  cells  all  over  the 
body  consume  oxygen  in  performing  their  various  func- 
tions.    Oxygen  is  a  very  important  element  that  easily 
combines  with  many  substances. 

2.  The   air   has    gained    a    large   amount  of   carbon 
dioxid.     When   the  foods   are   oxidized  in  the  cells  to 
furnish    heat   and   energy,  a   large  quantity  of    carbon 
dioxid  is  formed,  which  is  a  waste  and  must  be  removed 
from  the  blood.     There  seems  to  be  an  exchange  in  the 
lungs,  oxygen  going  into  the  blood  and  carbon  dioxid 
leaving  it. 

3.  Good  fresh  air  is  quite  free  from  organic  impuri- 
ties.    In  the  body  a  large  amount  of  these  wastes  is  con- 
stantly made  and  poured  into  the  blood.     These  wastes 
are  removed  in  part  through  the  lungs.     The  character- 
istic odor  of  exhaled  air  is  due  to  this  decaying  animal 
matter. 

4.  The  amount  of   watery  vapor  in  the   inhaled  air 
varies  from  time  to  time,  depending  upon  the  amount  of 


RESPIRATION  55 

moisture  in  the  atmosphere.  The  exhaled  air  is  always 
saturated,  i.e.  it  has  all  the  moisture  it  can  possibly  horld 
at  that  temperature. 

5.  The  temperature  of  the  air  we  breathe  varies  with 
the  time  of  day  and  season.  The  air  as  it  passes  from 
the  lungs  has  the  temperature  of  the  body,  about  ninety- 
eight  degrees  (98'  F.). 

Hence  we  are  constantly  taking  from  the  air  oxygen 
and  giving  in  exchange  carbon  dioxid  and  poisonous 
organic  substances.  It  is  the  presence  of  this  organic 
waste  that  makes  it  so  dangerous  to  rebreathe  the  same 
air  and  makes  ventilation  so  important. 

1.  Get  a  few  small  pieces  of  unslacked  lime  and  put  them  into  a 
fruit  jar.     Fill  the  jar  with  water,  and  set  it  away  for  a  day  or  two. 
When  the  lime  has  all  settled  to  the  bottom,  carefully  pour  off  the 
clear  water  into  another  bottle  and  label  it  limewater. 

2.  Exhale   air  into  the  limewater  and   observe  how   milky  the 
limewater  becomes. 

3.  Exhale  on  a  dry,  clean  mirror,  and  notice  how  the  moisture 
collects  on  it.     Have  you  ever  noticed  how  the  moisture  exhaled 
from  the  lungs  condenses  on  cold  frosty  mornings  ? 

4.  Exhale  on  a  thermometer  bulb  for  a  few  minutes  and  notice 
that  the  mercury  rises. 

54.  Rate  of  Breathing.  —  The  number  of  times  we 
breathe  per  minute  varies  with  age,  position  of  body, 
and  exercise.  The  rate  at  different  ages  is  about  as 
follows  :  — 

Infants  soon  after  birth 44 

Child  from  i  to  5  years 26 

Youth,  15  to  20  years -20 

Early  manhood,  20  to  25  years 19 

Manhood,  25  to  30  years 16 

Middle  life  to  old  age      .     .     . 18 


56  HUMAN   PHYSIOLOGY  CHAP. 

Count  the  number  of  respirations  per  minute  of  different  persons 
without  letting  them  know  what  you  are  doing.  How  does  the 
number  vary  with  age  ?  Exercise  ?  Position  of  body  ? 

The  average  rate  for  an  adult  when  reclining  is  about 
thirteen,  sitting,  about  nineteen,  and  standing,  about 
twenty-two. 

The  breathing  is  increased  very  much  when  we  run 
or  do  any  hard  physical  work.  Why  ?  We  know  that 
when  we  exercise  vigorously  the  muscle  cells  work 
harder.  They  need  more  food  and  oxygen  to  furnish 
the  energy  necessary  to  keep  up  the  exercise.  But 
you  will  remember  that  oxidation  manufactures  carbon 
dioxid.  When  we  run,  all  the  large  muscles  used 
pour  this  carbon  dioxid  and  other  wastes  into  the 
blood  very  fast.  Now,  if  we  did  not  breathe  faster  to 
remove  these  wastes,  they  would  accumulate  in  the 
blood  and  cause  disease  and  death. 

But  how  do  the  muscles  of  the  chest  know  that  they 
should  work  harder  to  remove  the  animal  wastes  ?  That 
is  a  hard  question  to  answer  in  a  simple  way.  The 
wastes  are,  of  course,  washed  along  in  the  blood  stream 
and  so  reach  all  parts  of  the  body.  When  they  come 
in  contact  with  a  group  of  nerve  cells  at  the  upper  end 
of  the  spinal  cord  they  act  like  a  poison  to  them.  The 
nerve  cells  send  a  command  to  the  muscles  of  the  chest 
by  means  of  several  nerves  and  tell  them  to  contract 
faster,  so  that  these  wastes  may  not  accumulate  in  the 
body.  Thus  we  see  that  the  rate  of  breathing  is  care- 
fully regulated  and  controlled  by  a  special  group  of 
nerve  cells. 


RESPIRATION  57 


SUMMARY   OF  THE   MAIN   POINTS 

1.  The  oxygen  of  the  air  is  necessary  to  cause  the  slow 
combustion  or  oxidation  of  the  foods  in  the  cells  of  the  body. 

2.  The  air  reaches  the  lungs  through  a  number  of  organs 
which  form  the  air  passages.     They  are  all  composed  of  plates 
and  rings  of  cartilage  held  together  by  connective  tissue,  and 
lined  with  a  mucous  membrane. 

3.  The  nasal  passages  are  large,  irregular,  winding  passages 
in  the  nose  that  warm  the  air,  remove  particles  of  dust  and  dirt, 
and  contain  the  nerves  of  smell.     We  should  breathe  through 
the  nose  rather  than  through  the  mouth. 

4.  The  pharynx  is  a  funnel-shaped  organ  back  of  the  nose 
and  mouth  from  which  there  are  seven  different  openings. 

5.  The  larynx  is  just  below  the  back  part  of  the  mouth  and 
serves  as  an  air  passage  and  as  the  organ  of  voice. 

6.  The  trachea  is  about  four  and  one  half  inches  long,  ex- 
tending from  the   larynx  to   the  two    bronchi.     It  is  usually 
called  the  windpipe. 

7.  The  bronchial  tubes  extend  to  the  lungs,  where  they  get 
smaller  and  lighter  until  they  terminate  in  very  small,  thin- 
walled  air  sacs. 

8.  The  lungs  are  the  central  organs  of  respiration.     They 
are  pinkish,  spongy,  elastic  masses  completely  filling  the  chest 
Each  lung  is  covered  with  a  closed  sac  called  the  pleura. 

9.  The   diaphragm,   intercostal   muscles,  and  the  muscles 
of  the  neck  work  together  and   enlarge  the  chest  at  regular 
intervals. 

10.  The  atmospheric  pressure  and   elasticity  of  the   lungs 
make  the  lungs  follow  the  chest  in  its  movements. 

11.  The  lungs  of  the  average  adult  hold  about  three  hun- 
dred and  thirty  cubic  inches  of  air.     At  each  ordinary  inspira- 
tion about  thirty  cubic  inches  of  air  is  inhaled. 


58  HUMAN   PHYSIOLOGY  CHAP,  v 

12.  The  exchange  of  gases  in  the  lungs  through  the  walls 
of  the  capillaries  and  air  sacs  is  called  osmotic  action. 

13.  Breathing    changes    the  temperature    and    composition 
of  the  air.     Rebreathing  the  same  air  is  dangerous  because  it 
contains  too  little  oxygen,  too  much  carbon  dioxid  and  organic 
poisons. 

14.  The  average  rate  of  breathing  per  minute  is  thirteen 
when  lying  down,  nineteen  sitting,  and  twenty-two  standing. 

15.  The  presence  of  carbon  dioxid  and   organic  wastes  in 
the  blood  irritates  the  nerve  cells  which  regulate  the  muscular 
movements  in  breathing. 


CHAPTER   VI 

HYGIENE   OF   RESPIRATION 

55.  Disease  Germs  in  the  Air.  —  Along  with  the  air 
there    may  be    inhaled    fine  dust,  injurious    gases,  and 
many  kinds  of  disease  germs  and  other  impurities  float- 
ing about  in  the  atmosphere.     Some  of  these  do  little 
or  no    harm,  but   others   irritate   the    delicate    mucous 
membrane  and  even  cause  disease.     Among  the  mala- 
dies  that   afflict   the   air   passages  or   enter   the  body 
through  them  are  the  following  :  colds,  catarrh,  adenoid 
growths,    bronchitis,    asthma,    pneumonia,    diphtheria, 
consumption,  mumps,  measles,    scarlet   fever,    chicken 
pox,  and  smallpox. 

Many  infectious  and  contagious  diseases  are  due  to 
little  germs  that  are  inhaled  and  then  attack  the  mucous 
membrane  directly  or  enter  the  blood  and  are  carried  to 
the  organs  in  which  they  can  best  do  their  deadly  work. 
We  call  these  " air-borne"  diseases.  Most  of  these 
maladies  could  be  avoided  if  all  people  realized  the 
value  of  pure  air  and  understood  the  nature  and  causes 
of  the  more  common  diseases  of  this  kind. 

56.  Diseases  of  the  Air  Passages.  —  No  organs  of  the 
body  are  more  subject  to  disease  than  the  air  passages. 
The   delicate  mucous  membrane  is  well  supplied  with 

59 


6o  HUMAN  PHYSIOLOGY  CHAP. 

small  blood  vessels  that  easily  become  gorged  with 
blood  (congested)  when  any  part  of  the  body  is  exposed 
to  cold.  The  phlegm  that  gathers  in  these  organs  when 
one  has  an  ordinary  cold  seems  to  be  a  natural  salve  to 
protect  the  inflamed  membrane  against  irritating  foreign 
substances. 

Catarrh  is  an  inflammation  of  the  nasal  passages  that 
continues  for  a  long  time  and  may  become  the  cause  of 
ulcers.  A  "cold  in  the  head"  is  due  to  an  inflamma- 
tion of  the  mucous  membrane  of  the  pharynx  and  the 
tubes  that  extend  to  the  ears  and  eyes.  When  the  con- 
gestion is  confined  to  the  larynx,  as  when  a  cold  makes 
it  difficult  or  impossible  to  talk,  we  call  it  laryngitis. 
A  similar  inflammation  of  the  trachea  and  bronchial 
tubes  is  known  as  bronchitis.  The  little  muscle  fibers 
of  the  bronchioles  that  lead  to  the  air  sacs  may  be- 
come irritated  and  contract  so  as 
to  prevent  the  air  from  entering  the 
sacs  as  freely  as  it  should ;  such  a 
condition  of  difficult  breathing  is 
sometimes  called  asthma. 

The    inflammation    may    not   re- 
main in  the  air  passages  only  but 
FIG.  28. -Bacteria of       extend  down  into  the  air  sacs  them- 

pneumonia  (Pratt). 

selves.  They  may  become  so  filled 
that  breathing  becomes  painful  and  difficult.  This  con- 
dition may  bring  on  the  disease  known  as  pneumonia. 

All  of  the  diseases  mentioned  are  not  mere,  conges- 
tions and  inflammations.  They  are  due  to  attacks  of 
certain  germs.  The  congestion  affords  an  excellent 


VI 


HYGIENE  OF   RESPIRATION 


6 1 


FIG.  29.  —  Bacteria  of 
consumption  (Pratt). 

In  the  state  of 


condition  for  these  little  germs  to  gain  a  foothold.     The 

air  in  temperate  climates  always  contains  large  numbers 

of  these  germs,  which  we  inhale  freely  every  day,  but 

which  are  harmless  as  long  as  the 

body  does  not  offer  them  a  favorable 

soil  in  which  to  grow  and  multiply. 
The   most   dreaded  and  fatal   of 

all  diseases  known  is  consumption. 

From  ten  to  twenty  per  cent  of  all 

deaths  in  temperate  regions  are  due 

to  this  terrible  disease  of  the  lungs. 

One  person  in  every  seven  falls  a 

victim  to  the  "great  white  plague." 

Massachusetts,  during  a  period  of  twenty  years,  statis- 
tics show  that  four- 
Evstachiantube  teen  per  cent  of  all 
deaths  reported  were 
due  to  consumption, 
and  that  the  mortality 
was  greatest  between 
the  ages  of  twenty 
and  thirty  years.  The 
germs  reach  the  lungs 
and  there  multiply  so 
rapidly  that  the  parts 
affected  soon  become 
useless. 
Adenoid  growths  occur  very  often  in  the  back  part  of 

the  nose  and  in  the  pharynx  of  young,  rapidly  growing 

children.     They  obstruct  the  nasal  passages  and  make 


FlG.  30.  —  Showing  the  location  of  adenoid 
growths  (Zuppke). 


62  HUMAN   PHYSIOLOGY  CHAP. 

nose-breathing  impossible.  Air  must  then  be  taken 
through  the  mouth.  If  these  growths  are  not  removed, 
they  may  become  so  large  as  to  fill  the  upper  part  of  the 
pharynx  and  impair  the  hearing  by  closing  the  tubes 
that  lead  to  the  ears.  All  who  find  it  difficult  to  inhale 
enough  air  through  the  nasal  passages  should  consult  a 
skillful  physician. 

57.  Sources  of  Impure  Air.  —  What  may  make  the 
atmosphere  impure  and  dangerous  to  breathe  ?  On  the 
seashore,  in  the  country,  and  on  mountains  the  air  is 
quite  fresh  and  invigorating,  but  there  are  many  ways 
of  polluting  the  air  in  our  homes  and  in  the  cities.  Let 
us  see  what  some  of  them  are. 

1.  Burning. — Whenever   wood,   coal,   oil,   coal  gas, 
etc.,  are  burned,  a  large  amount  of  impurity  is  produced, 
some  of  which  passes  off  into  the  air  as  carbon  dioxid 
and  other   gaseous   substances.     All  smokestacks  and 
chimneys    pour   volumes    of   such   impurities   into   the 
atmosphere. 

2.  Decaying.  — All  animal  and  vegetable  matter  allowed 
to  decay  pollutes   the    atmosphere  with    its    poisonous 
matter  for  a  long  distance. 

3.  BreatJiing.  —  Man  and    all    other   animals    exhale 
carbon  dioxid  and  organic  wastes  that  are  poisonous  to 
rebreathe. 

4.  Sewer  Gas.  —  If  the  plumber  has  not  done  his  work 
well,  air  from  the  sewer  escapes  in  the  house.     Such  air 
contains  very  dangerous  gaseous  compounds  and  various 
disease  germs  that  are  thrown  into  the  air  by  the  bubbles 
which  burst  on  the  surface  of  the  putrefying  sewage. 


vi  HYGIENE  OF  RESPIRATION  63 

5.  Factories.  —  The  manufacture  of  ammonia,  hydro- 
chloric acid,  and  other  things  by  chemical  works,  and 
the  making  of  glue,  candles,  leather,  and  bricks  pollute 
the  air  of  our  cities  with  dangerous,  nauseous  products. 

6.  Old  Wells  and  Close  Cellars.  —  The  carbon  dioxid, 
marsh  gas,  and   organic   impurities   that   form    at   the 
bottom  of  old  wells  and  in  close,  dark,  and  dirty  cellars 
are  responsible  for  many  diseases. 

7.  Marshes  and  Stagnant  Pools.  —  The  formation  of 
organic  matter   and    marsh  gas  by  the  slow  decay   of 
vegetables  in  damp,  swampy  places  makes  them  sources 
of  contamination.     Malarial  fevers    are    due   to   germs 
that  abound  in  such  localities. 

Many  other  causes  might  be  named  which  tend  to 
make  the  air  unfit  to  breathe  by  robbing  it  of  oxygen, 
by  pouring  into  it  useless  and  dangerous  gases,  and  by 
filling  it  with  disease-producing  germs  (bacteria).  It 
would  seem  that  with  all  these  sources  of  pollution  the 
air  would  become  utterly  unfit  for  breathing.  We  shall 
see  why  it  does  not. 

1.  Burn  a  candle  in  a  wide-mouthed  bottle.    When  it  goes  out 
add  a  little  clear  limewater  and  shake  thoroughly.     What  do  you 
infer  ? 

2.  In  the  same  way  try  the  burning  of  paper,  wood,  etc. 

3.  Test   the  gas   that   escapes   from    fermenting    liquids.      See 
section  37. 

58.  The  Air  Purified.  —  There  are  several  natural 
means  by  which  the  air  tends  to  purify  itself. 

i.  Diffusion.  —  All  of  the  gases  of  the  atmosphere  are 
kept  in  constant  motion  and  so  tend  to  become  equally 


64  HUMAN   PHYSIOLOGY  CHAP. 

mixed  throughout  the  entire  world  over  land  and  sea. 
Although  such  a  uniform  distribution  is  never  reached, 
yet  this  means  prevents  the  air  from  becoming  entirely 
unfit  for  breathing  in  certain  places.  If  it  were  not  for 
the  principle  of  diffusion  of  gases,  people  could  not  live 
in  large  cities. 

2.  Winds.  —  All  the  time  there  are  currents  of  air 
moving  from  place  to  place  which  not  only  aid  in  the 
mixing  of  gases  but  move  the  entire  body  of  air  and 
tend  to  distribute  the  temperature  equally. 

3.  Rain.  —  Gases,  dust,  and  other  impurities  are  taken 
up  by  the  raindrops  and  washed  out  of  the  air.     Snow 
in  the  winter  has  a  similar  purifying  effect.     The  mois- 
ture and  oxygen  of  the  air  change  many  impurities  of 
the  atmosphere  by  oxidizing  them  to  harmless  products. 

4.  Vegetation.  —  Plants  take  carbon  dioxid  from  the 
air,  and  water   from  the   ground  as    their  food.     The 
green  cells  of   the  leaves  change  these  two  substances 
into  starch  by  the  aid  of  the  heat  which  the  sun  fur- 
nishes.    When  the  plant  puts  carbon  dioxid  and  water 
together  to  form  starch,  it  has  quite  a  large  amount  of 
oxygen  which  it  does  not  need,  and  this  it  gives  back 
to  the  air.     The  plant  inhales  carbon  dioxid  and  exhales 
oxygen.     In  animals   the   very   opposite  occurs.     The 
plant  purifies  the  air  for  us,  and  we  purify  the  air  for 
the  plant. 

59.  Ventilation.  —  Everything  we  eat,  drink,  and  wear 
should  come  in  contact  with  life-giving,  germ-destroying 
oxygen  and  sunshine.  How  pale  and  sickly  a  plant 
looks  that  is  kept  in  a  dark,  close  room  !  The  rooms  in 


vi  HYGIENE   OF   RESPIRATION  65 

which  we  work  and  sleep  as  well  as  the  clothing  we 
wear  should  be  thoroughly  ventilated. 

The  subject  of  ventilation  would  require  no  attention 
if  we  lived  in  the  open  air  all  the  time.  But  how  can 
we  get  enough  fresh  outdoor  air  to  breathe  in  our  school- 
houses  and  homes  ?  This  is  really  not  a  simple  ques- 
tion to  answer,  although  one  of  great  importance.  At 
each  breath  we  exhale  about  thirty  cubic  inches  of  air 
or  about  five  hundred  cubic  inches  per  minute.  We 
should  not  rebreathe  the  air  exhaled,  for  it  contains  too 
much  injurious  matter;  but  after  it  has  mixed  with 
about  one  hundred  times  its  volume  of  fresh  air  it  is 
again  safe  to  inhale.  A  person  requires  then  about 
thirty  cubic  feet  of  air  per  minute.  For  forty  persons 
in  a  schoolroom  we  should  take  in  from  the  outside  at 
least  one  thousand  two  hundred  cubic  feet  of  fresh  air 
per  minute  and  allow  an  equal  volume  of  foul  air  to 
escape. 

Careful  estimates  show  that  there  should  be  an  allow- 
ance of  at  least  six  hundred  cubic  feet  of  space  for  each 
person  in  the  room. 

The  matter  of  ventilation  is  one  of  prime  importance 
and  should  receive  the  thoughtful  attention  of  those 
who  construct  private  and  public  buildings.  School- 
houses,  churches,  public  halls,  and  theaters  should  be 
provided  with  ventilating  flues  as  well  as  with  doors  and 
windows. 

Fill  a  pint  fruit  jar  with  water  and  enter  a  room.     Pour  out  the 
water  and  the  air  of  the  room  will  enter  to  fill  the  fruit  jar.     Now 
pour  two  tablespoonfuls  of  clear  limewater  into  the  fruit  jar,  cover 
F 


66  HUMAN   PHYSIOLOGY  CHAP. 

it  tightly  with  the  hand  and  shake  thoroughly.  If  the  limewater 
turns  milky  the  ventilation  needs  immediate  attention.  If  the  lime- 
water  is  not  changed  at  all,  the  amount  of  carbon  dioxid  in  the  air 
is  comparatively  small. 

60.   Method  of  Ventilation.  —  If   the  room  is   heated 
with  a  hot-air  furnace,  the  entrance  of  fresh  air  will  take 

Wcare  of  itself.  The  pure  air  from  out- 
side enters  the  furnace  jacket,  where  it 
is  warmed,  and  then  it  passes  up  into 
the  room.  Care  must  be  taken  to  keep 
the  foul-air  flues  open,  so  as  to  per: 
/\_  mit  the  bad  air  to  escape.  This  is  one 

of  the  most  satisfactory  means  of  heat- 
ing and  ventilating  at  the  same  time. 

If  the  room  is  Jieated  with  a  stove, 
you  must  provide  for  a  similar  circula- 
tion through  the  room.  Fresh  air  must 
come  in  from  outside,  pass  through  the 
room,  and  escape  as  fast  as  it  becomes 
>&W0  unfit  for  breathing.  How  can  this  be 
done  ?  Open  windows  are  dangerous, 

FIG.  31.  — Window  .       .  .,  .  ..  . 

ventilation  f°r  jt  1S  impossible  to  avoid  drafts  in 

(Zuppke).  some    part   of   the   room   in  very   cold 

weather.  A  simple  method,  if  the  room  is  large,  is  to 
fit  a  board  tightly  under  the  lower  sash  of  every  win- 
dow. It  should  be  as  wide  as  the  window  and  just  high 
enough  to  permit  good  circulation  between  the  two 
sashes,  as  shown  in  the  figure  above. 

Another  method  is  to  lower  the  upper  sash  and  pro- 
vide some  means  for  throwing  the  fresh  air  upward  as 


vi  HYGIENE  OF   RESPIRATION  67 

it  enters ;  or  the  lower  sash  may  be  raised  and  means 
provided  for  directing  the  entering  air  upward.  These 
are  inexpensive  but  quite  effective  means  of  ventilation. 
61.  Chest  Freedom. — The  air  we,  breathe  may  be 
perfectly  pure  and  fresh,  and  yet  the  cells  of  the  body 
may  suffer  because  they  do  not  receive  enough  oxygen. 
You  remember  that  the  chest  acts  like  a  pump  which 


Natural.  Deformed. 

FIG.  32.  —  Showing  a  natural  and  a  deformed  chest.     (From  Kellogg's  "  Out- 
line Studies.") 

at  every  natural  inspiration  pumps  about  thirty  cubic 
inches  of  air  into  the  lungs.  Now,  if  the  chest  does  not 
do  its  work  as  it  should,  an  abundance  of  good  whole- 
some air  may  be  present,  and  yet  only  a  small  amount 
get  into  the  lungs.  How  may  the  work  of  the  chest  be 
hampered  ?  In  the  first  place,  by  clothing  that  is  im- 
properly made  or  that  does  not  fit.  Clothing  may  be 
so  tight  about  the  waist  that  the  chest  cannot  enlarge 


68 


HUMAN   PHYSIOLOGY 


CHAP. 


freely.  A  child  may  be  so  accustomed  to  improper 
clothing  that  slowly  and  gradually  his  chest  becomes 
permanently  deformed. 

Careless  positions  in  standing  and  sitting  may  cause 
the  chest  to  become  so  deformed  as  to  make  natural 
breathing  impossible.  When  a  person  becomes  round- 
shouldered  and  flat-chested  the  upper  part  of  the  thorax 
cannot  enlarge  as  it  should.  The  result  is  that  the  apex 


Left  curz>e. 


Round  shoulders. 


FlG.  33.  —  Showing  deformed  chests.    (Drawn  by  H.  Meyer  from  photographs.) 

of  each  lung  remains  unused.  A  pupil  who  sits  day 
after  day  at  a  desk  that  is  either  too  high  or  too  low  soon 
finds  that  one  shoulder  is  higher  than  the  other  and  that 
the  spine  is  curved  to  the  right  or  to  the  left.  Under 
any  of  these  conditions  the  chest  cannot  expand  as  it 
should,  and  lung  diseases  are  easily  contracted. 

Sometimes  persons  are  born  with  small  or  deformed 
chests  and  are  more  likely  to  contract  the  diseases 
which  attack  the  lungs.  Consumption  is  probably 
seldom  if  ever  inherited,  although  weak  and  imperfectly 


vi  HYGIENE  OF   RESPIRATION  69 

developed  chests  frequently  are.  Weak  chests  may  be 
strengthened  by  regularly  taking  proper  respiratory 
gymnastics. 

62.  Proper  Breathing.  —  The  chest  may  be  enlarged 
up    and  down  by  the  action  of  the    diaphragm,  from 
front  to  back  by  the  action  of  certain  muscles  of  the 
neck,  and  from  side  to  side  by  the  use  of  the  muscles  of 
the   ribs.     Natural  breathing   exists    only  when   all  of 
these  muscles  work  as  they  should  and  cause  the  chest 
to  enlarge  in  all  of  these  directions.     Tight  clothing, 
bad  habits  in  standing  and  sitting,  and  improper  school 
desks  work  together  to  deform  the  chest  and  decrease 
its    capacity  for    breathing.     Proper   breathing    makes 
use  of  all  parts  of  the  lungs.     Among  civilized  people 
women  use  the  upper  part  of  the  lungs  chiefly,  while 
men  breathe  mostly  with  the  lower  part ;  among  savages 
this  difference  does  not  exist. 

63.  Alcohol.  — The  nerves  controlling  the  movements 
of  the  chest  and  the  size  of  the  blood  vessels  are  easily 
paralyzed  by  alcohol.    As  a  result  the  delicate  capillaries 
of  the  lungs  dilate  too  much,  causing  a  congestion  and 
inflammation,  which  tends  to  diminish  the  capacity  of 
each  little  air  sac  and  thus  reduce  the  total  lung  capacity. 
A  still  more  serious  effect  of  the  habitual  use  of  alco- 
holic   beverages   is    that    alcohol    gradually    diminishes 
the  power  of  the  capillaries  to  dilate ;  they  become  less 
and  less  responsive  to  the  ordinary  stimulation  of  the 
nerves.     We  can  now  understand  why  persons  who  use 
alcoholic  beverages  are  especially  liable  to  take  pneu- 
monia and  other  diseases  of  the  lungs. 


70  HUMAN   PHYSIOLOGY  CHAP. 


SUMMARY   OF  THE   MAIN   POINTS 

1.  The  air  always  contains  bacteria  which  get  into  the  air 
passages  and  lungs  and  may  cause  some  of  the  most  fatal  dis- 
eases known. 

2.  Exposure  to  drafts  and  colds  may  cause  congestion  in 
the  capillaries   of  the  mucous    membrane.     Such  congestions 
are    favorable    for  the    growth   and    development   of   harmful 
bacteria. 

3.  Among  the  diseases  of  the  air  passages  are  colds,  influ- 
enza, catarrh,  bronchitis,  adenoid  growths,  diphtheria,  asthma, 
pneumonia,  and  consumption. 

4.  The    atmosphere    contains    impurities    that    come    from 
various    sources,    as   combustion,    decay,    respiration,    sewage, 
factories,  old  wells  and  close  cellars,  marshes,  stagnant  pools, 
etc. 

5.  There  are  many  natural  agencies  at  work  to  purify  the 
atmosphere,    as    diffusion,   winds,   rain    and    snow,  growth    of 
plants,  etc. 

6.  The  exhaled   air  contains  impurities  enough  to  pollute 
several  times  its  volume  of  pure  air.     Therefore,  it  is  necessary 
for  each  person  in  a  room  to  have  about  thirty  cubic  feet  of 
fresh  air  to  breathe  every  minute. " 

7.  The  air  we  breathe,  the  food  we  eat,  the  water  we  drink, 
the  clothes  we  wear,  and  the  bed  we  sleep  in,  all  need  careful 
ventilation. 

8.  Buildings  in  which  many  persons  work  and  live  together, 
as  churches,  factories,  theaters,  and  schoolhouses,  need  to  have 
special  provisions  for  the  entrance  of  fresh  air  and  for  the  exit 
of  foul  air. 

9.  The  chest  should  be  free  to  expand  in  all  directions,  thus 
enabling  us  to  use  the  entire  lung  at  each  inspiration.     Proper 
breathing  makes  use  of  all  parts  of  the  lungs  constantly. 


vi  HYGIENE  OF   RESPIRATION  71 

10.  Clothing  tight  about  the  waist,  careless  postures  of  the 
body,  improper  school  desks,  and  a  naturally  small  and  weak 
chest  are  conditions  that  make  it  difficult  to  supply  the  blood 
with  a  sufficient  amount  of  oxygen. 

11.  Alcohol  tends  to  reduce  the  breathing  capacity  of  the 
lungs  by  causing  the    capillaries   of  the  lungs  to  dilate,  thus 
diminishing  the  size  of  the  air  sacs.     It  also  predisposes  the 
tissues  of  the  lungs  to  certain  diseases. 


CHAPTER   VII 


DIGESTION 


Mot/fh 


HMKr 

body.    (From  Mivart,  by  Gun- 

nison.) 


64.  Review.  —  We  have 
learned  that  each  cell  of  the 
human  body  must  have  foods 
to  keep  it  repaired  and  to 
give  it  heat  and  energy.  The 
materials  which  the  cells  can 
use  are  proteids,  carbohy- 
drates, fats,  salts,  water,  and 
oxygen.  We  have  seen  that 
oxygen  enters  the  blood 
through  the  lungs  and  that  it 
is  then  ready  to  be  carried  to 
all  the  tissues  of  the  body. 
We  must  now  learn  how  water 
and  solid  foods  get  into  the 
blood.  The  oxygen  of  the 
air  enters  the  blood  without 
being  changed  in  any  way, 
for  the  oxygen  in  the  blood 
is  just  like  the  oxygen  in  the 
atmosphere.  The  water  also 
mixes  with  the  blood,  un- 
72 


CHAP.  VII 


DIGESTION 


73 


changed.  But  pota- 
toes, beefsteak,  eggs, 
bread,  and,  in  fact, 
all  the  solid  food 
materials  must  be 
changed  very  much 
before  they  can  en- 
ter the  blood  and  be 
of  value  to  nourish 
the  cells.  We  shall 
now  find  out  how 
the  solid  foods  are 
changed  into  blood. 
65.  The  Alimen- 
tary Canal.  —  The 
air  reaches  the  blood 
through  a  series  of 
organs  called  air 
passages,  and  the 
other  foods  enter 
the  body  by  means 
of  a  series  of  organs 
which  together  con- 
stitute the  alimentary 
canal,  or  digestive 

tract.      The    alimen-         Fir"  35- —  The  alimentary  canal  (Zuppke). 

tary  canal  is  a  long  tube  that  extends  from  the  mouth 
to  the  end  of  the  large  intestine.  It  is  a  canal  through 
the  body,  with  enlargements  at  certain  places.  This 
tube  consists  of  the  mouth  with  the  teeth  and  tongue, 


74  HUMAN   PHYSIOLOGY  CHAP. 

the  pharynx,  the  gullet  or  oesophagus,  the  stomach,  and 
the  small  and  large  intestines. 

There  are  no  bones  and  cartilages  in  this  tube  as  are 
found  in  the  air  passages,  but  its  walls  are  made  up  of 
several  coats  that  extend  through  its  entire  length. 

(1)  On  the  outside  we  find  a  thin,  serous  covering  whose 
function  is  quite  like  that  of  the  pleura  of  the  lungs. 
It  serves  to  keep   the   surfaces   that  move  upon  each 
other   well    oiled    and    in    that    way    prevents    friction. 

(2)  The  next  is  a  heavy,  muscular  coat  consisting  of  two 
separate  layers  all  along  the  canal,  except  in  the  stomach 
where  there  are  three.    The  outer  layer  has  muscle  fibers 
that    run  lengthwise,   while  in  the   inner   they  are   all 
circular  or  extend  around  the  canal,  and  in  the  stomach 
the   fibers  of    the   third  layer   run  obliquely.     (3)   The 
third  is  a  very  thick  mucous  membrane  that  lines  the 
entire  digestive  tract.    This  canal  extends  from  the  mouth 
to  the  lower  end  of  the  spine,  but  it  is  so  coiled  up  that 
it  is  really  about  thirty  feet  long. 

Ask  your  butcher  to  get  a  pig's  stomach  for  you.  In  size,  shape, 
and  general  structure  it  is  quite  like  man's.  Study  the  various  coats 
as  carefully  as  you  can.  Notice  the  velvety  mucous  membrane  on 
the  inside. 

66.  Glands.  —  A  number  of  very  important  organs 
called  glands  are  found  along  the  alimentary  canal. 
These  glands  pour  certain  fluids  into  the  canal,  which 
aid  in  changing  solid  foods  into  blood.  Such  organs  are 
the  salivary  glands  of  the  mouth,  the  gastric  glands  of 
the  stomach,  the  intestinal  glands,  the  pancreas,  and  the 
liver. 


DIGESTION 


75 


To  increase  the  surface  that  can  produce  such  fluids, 
the  mucous  membrane  may  become  folded  up  in  va- 
rious ways,  giving  rise  to  the  different  kinds  of  glands. 
While  the  glands  differ  much  in  their  outward  appear- 
ance and  size,  all 
have  the  same 
general  structure 
and  all  take  ma- 
terial from  the 
blood  to  manufac- 
ture important 
body  fluids  which 
perform  special 
functions. 

The  important 
thing  to  remem- 
ber is  that  a  gland 
is  merely  a  thick 
mucous  m  em- 
brane,  either 
straight  or  folded 
in  some  way,  con- 
taining many 
blood  vessels  and 


FJG.  36.  —  Showing  the  structure  of  glands. 
Modified  from  Huxley.     (Zinns.) 


nerves,  and  hav- 
ing the  power  to 
separate  from  the  blood  important  fluids  called  secretions. 
67.  The  Mouth.  —  The  mouth  is  the  first  organ  to 
receive  the  food.  It  is  a  rather  irregular-shaped  cavity 
extending  from  the  lips  in  front  to  the  soft  palate  be- 


76  HUMAN   PHYSIOLOGY  CHAP. 

hind.  On  the  sides  it  is  bounded  by  the  cheeks,  above 
by  the  hard  palate,  and  below  by  the  muscles  and  con- 
nective tissues  that  form  the  floor.  It  contains  the 
teeth  and  the  tongue,  two  very  important  organs  of 
digestion,  and  receives  the  saliva  through  a  number  of 
small  ducts  leading  from  the  three  pairs  of  salivary 
glands.  The  tonsils  are  two  olive-shaped  organs,  one 
on  either  side,  at  the  back  part  of  the  mouth.  They 
produce  a  fluid  that  probably  helps  in  swallowing. 

In  the  mouth  the  food  is  cut  and  ground  up  by  the 
teeth,  mixed  with  saliva,  moved  about  by  the  tongue, 
and  finally  pushed  back  into  the  pharynx. 

Study  carefully  your  own  mouth  as  to  shape,  size,  and  organs,  as 
teeth,  tongue,  tonsils,  and  palate.  This  may  easily  be  done  with 
the  aid  of  a  small  mirror. 

68.  The  Teeth.  —  At  birth  a  child  has  no  teeth.  The 
first  set  begins  to  appear  at  the  age  of  from  six  to  ten 
months  and  to  disappear  at  about  the  sixth  or  eighth 
year.  These  are  called  milk  teeth.  This  set  consists  of 
twenty  teeth  —  ten  in  each  jaw.  The  four  flat,  cutting 
teeth  are  called  incisors ;  the  one  sharp,  tearing  tooth  on 
either  side  of  the  incisors  is  the  canine ;  and  the  two 
double  grinding  teeth  back  of  each  canine  are  the 
molars. 

Is  it  not  strange  that  this  set  should  disappear  in 
youth  and  another  take  its  place  ?  Yes,  but  we  shall 
understand  why  when  we  learn  that  a  tooth  does  not 
grow  larger  after  it  is  once  fully  cut.  Our  hands,  feet, 
and  heads  grow,  but  our  teeth  do  not.  A  bone  grows 


VII 


DIGESTION 


77 


and  when  broken  has  the  power  to  repair  itself,  but  a 
tooth  does  not  The  milk  teeth  are  too  soft  and  delicate 
to  do  the  work  which  the  teeth  must  do  later  in  life. 

The  second  or  permanent  set  contains  thirty-two 
teeth  when  complete,  but  the  last  four,  known  as 
the  wisdom  teeth,  appear  late,  usually  between  the 
ages  of  seventeen  and  twenty-five  years.  In  addition 


FlG.  37. — Showing  permanent  teeth.     (From  Heitzmann's  "  Anatomy.") 
i,  2,  incisors;  3,  canine;  4,  5,  bicuspids;  6,  7,  8,  molars. 

to  the  twenty  of  the  first  set,  the  second  has  three 
more  molars  on  either  side  in  each  jaw,  so  that  an 
adult  has  four  incisors,  two  canines,  four  premolars  or 
bicuspids,  and  six  molars  in  each  jaw.  These  are  all 
larger,  stronger,  and  more  durable  than  the  milk  teeth. 

Get  from  a  dentist  a  handful  of  teeth.  Ask  him  to  saw  one 
crosswise  and  another  lengthwise  to  show  the  general  structure. 
Make  drawings  and  describe  one  of  each  class. 


HUMAN   PHYSIOLOGY 

CENTRAL  INCISORS 


CHAP. 


LATERAL  INCISOR 

CUSPID  OR  CANINE 
FIRST  BICUSPID 
SECOND  BICUSPID 


OR  WISDOM 


FIG.  38.  —  Upper  jaw,  showing  permanent  teeth  in  place.     (From  Hopkins' 
"  Care  of  the  Teeth."     D.  Appleton  &  Co.) 

69.  Structure  of  the  Teeth. —The  external  appear- 
ance shows  three  parts  :  the  crown,  or  the  visible  portion 
projecting  beyond  the  gum ;  the  root,  or  the  portion 
hidden  in  the  gum ;  and  the  neck,  or  narrow  border 
between  the  crown  and  the  root. 

A  tooth  sawed  through  the  middle  from  crown  to 
root  shows  that  it  is  made  of  four  different  things.  The 
main  part  of  the  framework  of  a  tooth  is  a  bonelike 
substance  called  dentine.  The  dentine  of  the  root  is 
covered  with  cement  and  that  of  the  crown  with  a 
very  hard,  highly  polished  substance,  called  enamel. 
Enamel  is  the  hardest  substance  in  the  body ;  it  serves 
to  protect  the  tooth.  There  are  no  blood  vessels  and 
nerves  in  the  enamel,  and  for  tJiat  reason  a  tootJi  cannot 


VII 


DIGESTION 


79 


repair  itself.     We  should  be  very  careful  not  to  crack 
or  in  any  way  injure  the  enamel. 


FIG.  39.  —  Showing  how  the  upper  and  lower  teeth  fit  together.     (From 
Hopkins'  "  Care  of  the  Teeth."     D.  Appleton  £  Co.) 

There  is  a  large  space  in  the  middle  of  the  dentine, 
called  the  pulp  cavity,  that  is  filled  with  connective 
tissue,  blood  vessels,  and 
nerves.  At  the  very  tip  of 
the  root  we  find  a  small  open- 
ing, through  which  the  blood 
vessels  and  nerves  enter  the 
tooth.  It  is  by  means  of  these 
vessels  that  the  central  por- 


Crown 
Neck 

/foot 


FIG.  40.  —  Showing  the  structure 
of  a  tooth  (Zinns). 


8o 


HUMAN   PHYSIOLOGY 


CHAP. 


tion  is  nourished.  A  dead  tooth  is  one  in  which  the 
dentist  has  taken  out  the  nerve  and  blood  vessels  and 
has  filled  the  root  with  something  else. 


FIG.  41.  —  Showing  how  the  blood  vessels  and  nerves  reach  the  teeth,  i,  2,  in- 
cisors ;  3,  canine;  4,  5,  bicuspids;  6,  7,  8,  molars;  a,  vein;  b,  artery; 
c,  nerve ;  d,  vein,  artery,  and  nerve.  (From  Johonnot  and  Bouton.) 

70.  Mouth  Digestion. — The  large,  strong  muscles  of 
the  cheeks  enable  us  to  use  the  teeth  for  biting,  tearing, 
crushing,  and  grinding  the  solid  foods.  Cooking  has 
helped  to  soften  the  foods,  yet  in  order  to  dissolve  them 
it  is  necessary  to  chew  every  mouthful  thoroughly.  It 
is  said  of  W.  E.  Gladstone,  the  great  English  statesman, 


VII 


DIGESTION 


81 


who  lived  to  be  a  very  old  man  and  yet  possessed  the 
vigor  of  manhood  to  his  very  end,  that  he  always  chewed 
every  mouthful  thirty-three  times. 

The  saliva,  or  spittle,  is  poured  into  the  mouth  while 
the  food  is  being  masticated  and  is  well  mixed  with  it. 
The  saliva  is  very  useful,  as  it  keeps  the  mouth  moist  all 
the  time,  aids  in  swallowing,  and  begins  the  digestion 
of  starchy  foods.  Now,  if  we  chew  well  and  eat  slowly, 
the  saliva  has  an  opportunity  to  act  on  a  large  amount 
of  starch. 

The  proteids  and  fats  are  not  changed  in  the  mouth 
except  that  they  are  broken  up  or  ground  into  fine  par- 
ticles and  so  prepared  for 
the  other  digestive  fluids. 
Most  of  the  salts  and  sugars 
are  dissolved  in  the  saliva 
and  are  then  ready  to  enter 
the  blood. 

Where  does  the  saliva 
come  from  ?  The  three 
glands  shown  in  the  dia- 
gram manufacture  it.  They 


are  \hz  parotid,  a  little  be- 
low and  in  front  of  the 
ears ;  the  submaxillary ,  at 
the  angles  of  the  lower 
jaw;  and  the  sublingual, 
in  the  floor  of  the  mouth. 


FIG.  42.  —  Showing  salivary  glands. 
(From  Huxley.)  a,  sublingual, 
b,  submaxillary  glands  with  their 
ducts  opening  under  the  tongue  at 
d  ;  c,  parotid  gland  with  its  duct 
opening  at  e. 

These  glands  pour  three  of 


four  pints  of  saliva  into  the  mouth  daily.     Chewing  and 
talking  cause  the  saliva  to  flow  freely.     Tasting,  seeing, 


HUMAN   PHYSIOLOGY 


CHAP. 


smelling,    and   even   talking   about   foods    makes 
mouth  water,"  especially  when  one  is  hungry. 


the 


1.  Put  into  a  test  tube  or  small  bottle  a  little  boiled  starch,  a  little 
saliva,  and  about  twice  as  much  water.     Shake  it  up  well  and  heat  it 
just  a  little  (not  over  100°  F.).     After  a  few  minutes  add  iodine  and 
notice  that  the  color  is  not  blue,  showing  that  there  is  no  starch 
present     What  has  changed  the  starch  ? 

2.  Repeat  the  experiment,  taking  raw  starch.     What  is  the  in- 
ference ? 

3.  In   place  of  iodine,  add   Fehling's  solution,  which    may  be 
obtained  at  a  drug  store,  and  boil  it  for  a  moment.     The  precipita- 
tion of  copper  shows  that  sugar  is  present.     The  starch  has  been 
changed  to  sugar. 

71.    Swallowing.  —  After    the    food    has    been    thor- 
oughly chewed  and  moistened  with  saliva  it  is  ready 

to  go  into  the  stom- 
ach. The  movement 
through  the  pharynx 
and  oesophagus  into 
the  stomach  is  called 
swallowing  or  deglu- 
tition. The  food  does 
not  fall  through  this 
tube,  because  one  can 
swallow  lying  down 
or  even  standing  on 

his     head.        Did    yOU 


Larynx 
(Esophagus 


FIG.  43.  —  The  beginning  of  the  food  and  air 
passages  (Zuppke). 

drinking  from  a  pail  on  the  ground  ?     The  water  goes 
up  into  the  stomach  in  this  case. 

The  tongue  presses  up  against  the  hard  palate  and 


VII 


DIGESTION 


pushes  the  food  into  the  back  part  of  the  mouth ;  the 
soft  palate  rises  to  close  the  opening  into  the  nose ;  the 
epiglottis  closes  the  opening  into  the  larynx  and  tra- 
chea ;  and  the  muscles  of  the  back  part  of  the  mouth 
contract  and  push  the  food  into  the  pharynx.  The  food 
is  now  in  the  pharynx,  and  there  is  but  one  opening  by 
which  it  can  leave.  The  mouth,  nose,  and  larynx  are 
all  closed.  The  muscles  of  the  pharynx  contract  and 


FlG.  44.  —  Food  in  the  pharynx  in 
swallowing  (Zuppke). 


food 


FlG.  45.  —  Food  in  the  oesophagus  on 
its  way  to  the  stomach  (Zuppke). 


crowd  the  food  down  into  the  oesophagus.  Sometimes 
it  happens  that  a  particle  of  food  gets  into  the  larynx 
and  trachea,  and  it  is  only  by  violent  coughing  that  it 
can  be  expelled. 

The  cesopJiagus  is  a  tube  about  nine  inches  long,  ex- 
tending from  the  pharynx  to  the  stomach  and  is  closed 
except  while  food  is  actually  passing  through  it.  By 
the  action  of  its  muscular  fibers,  which  we  have  learned 
run  both  longitudinally  and  circularly,  the  foods  are 


84 


HUMAN  PHYSIOLOGY 


CHAP. 


Cardiac 


pushed  along  through  the  oesophagus  into  the  stomach. 
A  similar  muscular  action  occurs  in  the  other  organs  of 
the  alimentary  canal. 

72.  Stomach  Digestion. — The  stomach  is  the  greatest 
enlargement  of  the  alimentary  canal,  being  about  ten 
inches  long  and  from  four  to  six  inches  across  and  hav- 
ing a  capacity  of  about  four  pints.  It  is  located  just 

below  the  diaphragm, 
with  the  larger  end 
(the  fundus)  to  the 
left  side.  It  has  an 
opening  for  the  food 
from  the  oesophagus 
to  enter,  called  the 
cardiac  orifice,  and 
one  for  the  food  to 
pass  out  into  the  in- 
testines, called  the 
pyloric  orifice.  These 
FIG.  46. -Outside  of  the  stomach,  front  openings  are  carefully 

view.     (From  Heitzmann's  "Anatomy."         guarded      by     Strong, 

circular    muscles,    so 

that  after  the  food  enters  the  stomach  it  cannot  leave 
until  it  is  thoroughly  digested.  Then  the  pylorus  re- 
laxes, and  the  mass  slowly  enters  the  intestines. 

The  stomach  differs  from  the  other  organs  of  the 
digestive  tube  in  that  it  has  tJirce  layers  of  muscles 
instead  of  two;  the  longitudinal  on  the  outside,  the 
circular  next,  and  the  oblique  or  transverse  on  the  in- 
side. The  mucous  lining  is  quite  thick  because  it  is 


VII 


DIGESTION 


folded  up  to  form   pocket-like  glands   over  the  entire 
surface. 

The  millions  of  these  little  glands  pour  a  fluid  into 
the  stomach,  called  gastric  juice.  This  fluid  is  very  im- 
portant to  digestion,  as  it  contains  an  acid  and  a  sub- 
stance called  pepsin,  that  together  can  digest  proteids. 
It  is  estimated  that  from  ten  to  twenty  pints  of  gastric 
juice  are  made  every 
twenty-four  hours.  As 
soon  as  the  food  enters 
the  stomach  the  gastric 
juice  begins  to  ooze 
from  the  mouths  of 
these  little  glands,  and 
the  muscles  commence 
to  contract  lengthwise, 
then  crosswise  and 
transversely.  This  vig- 
orous  churning  motion, 
which  is  kept  up  for 
several  hours  after  each 
full  meal,  so  completely 
mixes  the  foods  and  gastric  juice  that  the  entire  mass 
becomes  acid  and  of  a  uniform,  thick  soupy  consistency, 
having  a  grayish  color.  The  proteids,  like  beefsteak, 
cheese,  and  eggs,  are  changed  into  peptones  by  the 
chemical  action  of  the  acid  and  the  pepsin.  The  entire 
mass  is  then  known  as  chyme. 

If  we  chew  the  foods  carefully,  eat  slowly,  and  do 
not  overload  the  stomach,  it  will  do  its  work  easily  and 


Fio.  47.  —  Inside  of  the  stomach,  front 
view.  (From  Heitzmann's  "  Anatomy." 
Becker.) 


86 


HUMAN   PHYSIOLOGY 


CHAP. 


771 


well.  But  if  the  pieces  are  too  large  or  the  amount  too 
great  the  juice  cannot  get  at  the  foods  as  it  should,  and 
the  muscles  get  tired  out  before  all  the 
foods  are  dissolved.  The  stomach  is 
a  hard-working  organ,  but  it  should 
not  be  abused.  After  it  has  worked 
hard  for  three  or  four  hours  it  should 
get  some  rest  before  the  next  meal, 
so  that  it  will  be  ready  to  do  its  work 
as  it  should.  If  the  stomach  is  not 
abused,  a  person  will  always  be  hun- 
gry at  meal  times. 

The  stomach  is  a  very  important 
organ  of  digestion,  for  it  serves  as  a 
storehouse  for  foods,  dissolves  pro- 
teids,  and  destroys  many  kinds  of 
disease  germs  by  means  of  its  acid  ; 
and  yet  a  person  can  live  without  a 
stomach.  In  a  few  cases  of  serious 
diseases  the  stomach  has  been  entirely 
removed.  The  oesophagus  was  sewed 
directly  to  the  intestines,  and  the 
person  recovered  and  lived  for  years 
afterwards.  We  see  that  it  is  possi- 
ble for  a  person  to  live  without  a  stomach.  That  is 
because  the  digestive  fluids  of  the  small  intestine  can 
do  all  that  the  gastric  juice  does.  But  a  person  who 
has  had  his  stomach  removed  cannot  eat  as  much  at 
one  time  as  he  could  before,  and  hence  he  is  obliged  to 
take  food  at  shorter  intervals. 


-P 


FIG.  48.  — One  of  the 
glands  which  manu- 
factures gastr  i  c  j  uice. 
( From  Huxley.  ) 
D,  mouth  of  the 
gland;  m,  epithelial 
cells;  c,  central  cells 
which  make  pepsin ; 
p,  parietal  cells 
which  make  acid. 


VII 


DIGESTION 


TABLE  SHOWING  THE  TIME  REQUIRED  TO  DIGEST  CERTAIN  FOODS 
IN  THE  STOMACH 


FOODS 


TIME 

IN 

HOURS 
.  i 


Rice,  boiled 

Tripe,  soused i 

Pigs'  feet,  soused  .     .     .     .  i 

Soup  (barley) i^ 

Salmon  trout,  boiled  or  fried  1 1 

Apples,  sweet,  raw      ...  i  \ 

Venison,  steaks,  broiled  .     .  i  \ 

Eggs,  fresh,  whipped .     .     .  ij 

Milk,  boiled 2 

Codfish,  cured,  dried  ...  2 

Cabbage,  raw 2 

Tapioca,  boiled      ....  2 

Liver,  broiled 2 

Turkey,  roasted     .     .     .     .  2| 

Milk,  raw 2.\ 

Potatoes,  baked  or  roasted  .  2\ 

Gelatin,  boiled \\ 

Goose,  roasted 2i 


Hash,  meat,  vegetables 
Lamb,  broiled  . 
Oysters,  fresh,  raw 
Pig,  roasted  .... 
Chicken,  roasted    .     . 
Corncake,  baked     .     . 


2| 

21 
21 
21 
2| 


FOODS 

Beefsteak,  broiled  .  .  . 
Apple  dumpling  .  .  . 
Chicken  soup  .... 
Eggs,  soft  boiled  .  .  . 
Mutton,  broiled  or  boiled 
Pork,  stewed  .... 
Oysters,  stewed  .  .  ^ 
Beef,  roasted  .  .  .  .' 
Bread,  wheat  .  .  .  . 

Butter 

Eggs,  fried  or  hard  boiled 
Beef,  fried  .  • .  .  .  . 
Duck,  domestic,  roasted . 
Salmon,  boiled .... 
Veal,  roasted  .... 

Cheese 

Pork,  fried 

Cabbage,  boiled 
Duck,  wild,  roasted    . 
Pork,  boiled      .     . 
Veal,  fried    .     .     . 
Pork,  roasted    .... 
Suet  beef,  boiled    . 


TIME 

IN 
HOURS 

•  3 

•  3 

•  3 

•  3 

•  3 

•  3 

•  3i 

•  3i 

•  3* 


4i 

41 

41 
5i 
5* 


These  observations  were  made  by  Dr.  Beaumont  in 
his  treatment  of  Alexis  St.  Martin,  who  had  a  gunshot 
wound  which  left  an  opening  into  the  stomach  from  the 
surface  of  his  body.  The  doctor  was  able  to  make 
many  interesting  and  very  important  observations,  for  he 
could  look  into  the  stomach  .at  any  time  and  study  the 


88  HUMAN  PHYSIOLOGY  CHAP. 

gastric  juice  and  its  action  on  the  various  foods.  Similar 
observations  have  been  made  in  other  cases  since. 

Get  a  few  grains  of  pure  pepsin  from  the  drug  store  and  make 
some  artificial  gastric  juice  by  mixing  together  one  grain  of  pure 
pepsin,  four  tablespoonfuls  of  warm  water,  and  about  ten  drops  of 
strong  hydrochloric  acid.  Label  it  gastric  juice.  It  is  now  ready 
for  use. 

1 .  Put  some  gastric  juice  into  a  small  bottle  or  test  tube  and  add 
soft-boiled  egg.     Watch  carefully  for  ten  or  fifteen  minutes. 

2.  Repeat,  using  a  few  fibers  of  raw  beefsteak.     Notice  carefully 
what  happens. 

3.  Repeat,  using  still  other  proteid  foods.     What  do  you  learn 
from  these  experiments  ? 

73.  Intestinal  Digestion.  —  The  portion  of  the  ali- 
mentary canal  into  which  the  foods  pass  from  the 

stomach  is  called  the  intes- 
tines. The  intestines  begin  at 
the  smaller  and  lower  end  of 
the  stomach  at  the  right  side 
and  form  the  remainder  of  the 

FlG.   40.  —  Small    intestine    cut         -,.         ,.          ,     -,  ,-,-,,        r 

open  to  show  the  folds  of  the     digestive  tube.     The  first  por- 
mucous  membrane.  (Drawn     tion  or  small  intestine  is  about 

by  Mater.)  _c          /•  j  / 

twenty- five  feet   long  and  one 

inch  in  diameter,  while  the  second  or  large  intestine  is 
about  five  feet  long  and  two  inches  in  diameter.  The 
intestines  consist  of  an  outer,  thin  serous  coat,  of  a 
middle,  muscular  coat  having  two  layers  of  fibers  (the 
longitudinal  and  the  circular),  and  of  an  inner,  very 
heavy  lining  of  mucous  membrane.  The  entire  wall 
varies  in  thickness  from  one  sixteenth  to  one  eighth  of  an 
inch.  The  tube  is  very  much  coiled  up  in  the  abdomen, 


VII 


DIGESTION 


as  can  be  seen  from  Figure  35.  We  see  that  the  large 
intestine  extends  up  to  the  liver  at  the  right  side,  across 
the  abdomen  in  front  of  and  below  the  stomach,  and 
down  at  the  left  side.  These  three  parts  are  known  as 
the  ascending,  the  transverse,  and  the  descending  colon. 
The  last  portion  of  the  large  intestine  is  the  rectum. 

The  mucous  membrane  of  the  intestines  has  millions 
of  tubelike  glands  all  over  it ;  they  are  important,  as  they 
produce  a  fluid,  the  intestinal  juice,  which  helps  to  digest 
the  starchy  foods.  The  intestinal  juice  also  helps  to  pre- 
pare the  acid 
foods  as  they 
come  from  the 
stomach  for 
the  digestion  in 
the  intestines. 

On    the    left 


Pa/? erect  fie  dt/ct 


FIG.  50.  —  The  pancreas,  front  view  (ZuppkeJ. 


side  of  the  body,  just  below  the  stomach,  is  the  most 
important  digestive  gland  of  the  body.  It  is  the/#;/- 
creas,  or  abdominal  sweetbread.  The  pancreas  is  pinkish 
yellow  in  color,  about  six  inches  long  and  two  inches  wide. 

A  duct  which  runs 
the  entire  length 
of  the  pancreas 
from  left  to  right 
empties  into  the 
small  intestine  a 
little  below  the  py- 


FlG.  51.  —  The  pancreas  cut  open  to  show  the 
ducts  (Zuppke). 


lorus.     The  chief  business  of  the  pancreas  is  to  manu- 
facture a  liquid  called  pancreatic  juice,  which  is  poured 


90  HUMAN  PHYSIOLOGY  CHAP. 

into  the  intestines  through  its  duct.  The  pancreatic 
juice  is  the  most  important  digestive  fluid,  for  it  contains 
substances  which  act  upon  starches  and  proteids,  and 
besides  it  has  a  substance  that  can  act  upon  fats  and 
oils,  changing  them  into  an  emulsion,  or  into  soap.  The 
pancreatic  juice  does  all  that  the  other  juices  do  and 
does  it  better  and  more  quickly.  The  pancreatic  and 
intestinal  juices  complete  the  process  of  digestion,  doing 
what  was  poorly  done  or  left  undone  by  the  other  di- 
gestive fluids. 

Gal  I  sac 

A 

Bile  duct 
Artery 
eft  lobe 


FIG.  52.  —  Under  surface  of  the  liver.    -Modified  from  Heitzmann.     (Becker.) 

The  liver,  located  on  the  right  side  just  over  the 
stomach,  is  the  largest  gland  of  the  body.  It  is  dark 
brown  in  color  and  weighs  between  three  and  four 
pounds.  This  large  gland  is  very  important,  for  it  does 
many  useful  things.  One  of  the  functions  of  the  liver 
is  to  manufacture  a  fluid  called  bile.  The  bile  is  poured 
into  the  intestines  through  the  bile-duct,  which  unites 
with  the  duct  from  the  pancreas,  and  together  they 


vii  DIGESTION  91 

pierce  the  intestine  about  two  inches  below  the  pylorus. 
Bile  is  made  all  the  time,  and  when  there  is  no  food  in 
the  intestines,  it  is  stored  up  in  a  little  bag  called  the 
gall-bladder.  This  is  located  on  the  under  surface  of  the 
liver,  with  the  larger  pear-shaped  end  toward  the  front. 

Bile  is  of  a  golden  yellow  color  in  man  and  has  a  very 
bitter  taste.  About  two  or  three  pints  are  manufactured 
daily.  It  is  not  able  to  digest  food  alone,  but  it  is  very 
important  because  .it  makes  the  pancreatic  juice  work 
much  better.  One  of  the  chief  functions  of  the  bile  is 
to  aid  the  pancreatic  juice  in  breaking  up  the  fat  into 
very  small  droplets  that  can  enter  the  blood.  It  stimu- 
lates the  muscles  of  the  intestines  to  more  vigorous 
action.  Part  of  the  bile  is  a  waste  product  of  the  liver, 
which  is  excreted  through  the  intestines. 

Thus  we  see  that  the  small  intestine  is  a  very  impor- 
tant place  for  the  digestion  of  foods.  Here  we  find  the 
intestinal  juice,  the  pancreatic  juice,  and  the  bile,  all 
active  in  changing  the  foods  not  yet  dissolved  so  that 
they  may  pass  through  the  walls  of  the  intestines  into 
the  bloodvessels.  The  act  of  digestion  is  now  complete. 
The  contents  of  the  small  intestine  has  a  milklike 
appearance,  and  the  entire  mass  is  known  as  chyle.  It 
is  now  ready  for  absorption. 

Get  a  few  grains  of  pancreatin,  dissolve  it  in  a  pint  of  water,  and 
add  a  little  baking  soda. 

1.  Test  its  action  upon  soft-boiled  egg,  shreds  of  raw  beefsteak, 
or  crumbs  of  cheese.     Keep  the  solution  warm  for  fifteen  or  twenty 
minutes. 

2.  Test  its  action  upon  boiled  starch. 

3.  Put  pancreatic  juice  into  a  test  tube  or  small  bottle  and  add  a 


92  HUMAN  PHYSIOLOGY  CHAP. 

little  oil.  Shake  thoroughly  for  a  minute  and  notice  that  the  oil  is 
changed  to  a  creamy  liquid,  called  an  emulsion.  Milk  is  a  good 
example  of  an  emulsion.  Lather  is  an  emulsion. 

74.  Places  of  Digestion.  — We  may  sum  up  the  places 
of  the  digestive  changes  as  follows:  (i)  In  the  mouth 
the  foods  are  cut,  ground,  and  softened,  and  some  of  the 
starchy  material  is  changed  into  sugar  by  the  action  of  the 
saliva.     (2)  In  the  stomach  a  large  amount  of  food  may 
be  stored  up  for  digestion,  most  of  the  foods  are  soft- 
ened by  the  churning  action  of  the  muscles,  and  some 
of  the  proteids  are  dissolved  by  the  action  of  the  gastric 
juice.     (3)  In  the  small  intestine  the  starchy  foods  are 
all  converted  into  sugars,  proteids  are  dissolved,  and  fats 
and  oils  are  broken  up  into  small  droplets  so  that  they 
may  enter  the  blood. 

75.  Peristalsis.  —  We   have   learned    that    the    food 
passes  through  the  oesophagus  by  a  peculiar  contrac- 
tion of  the  longitudinal  and  circular  muscles  to  which 
is  given  the  name  peristalsis.     The  stomach  churns  the 
food    by  constantly  throwing  it  back    and    forth,    now 
pressing  in  one  direction  and  now  in  another. 

In  the  small  intestine  there  is  a  muscular  movement 
which  thoroughly  mixes  the  foods  with  the  various 
digestive  fluids  and  also  forces  the  contents  along 
through  the  winding  course  of  the  canal.  As  the  food 
is  thus  moved  along  from  the  mouth  through  the  various 
parts  of  the  alimentary  canal,  its  bulk  is  increased  by 
the  addition  of  saliva,  gastric  juice,  bile,  pancreatic 
juice,  and  intestinal  juice,  and  it  becomes  more  and  more 
nearly  liquid.  The  only  solids  found  in  the  chyle  are 


VII 


DIGESTION 


93 


the  indigestible  material  that  formed  part  of  the  foods, 
as  shreds  of  elastic  tissue  and  hairs  from  meats,  husks 
or  coverings  of  grains  of  corn,  wheat,  oats,  peas,  and 
beans,  the  coloring  matter  of 
all  greens  and  vegetables, 
the  hard  vegetable  capsules 
that  cover  the  granules  of 
starch  in  potato,  corn,  etc., 
the  seeds  of  small  fruits,  and 
pieces  of  food  that  were  not 
ground  fine  enough  by  the 
teeth.  The  liquid  is  absorbed 
into  the  blood,  but  the  solids 
pass  on  into  the  large  intes- 
tine and  are  expelled  from 

,1        i      j       j    -I      i         ,  i  •  •         FIG.  S3.  —  Showing  the   valve   be- 

the  body  daily  by  this  peri- 

J  J       J  tween   the  small  and   large  m- 

GtaltlC  motion.  testines.     (Drawn  by  Mater.) 


fa/re. 


SUMMARY   OF  THE   MAIN   POINTS 

1.  The  alimentary  canal  is  a  long,  muscular  tube  with  en- 
largements at  certain  places  in  which  the  solid  foods  are  dis- 
solved so  that  they  can  enter  the  blood. 

2.  A  gland  is  a  mucous  membrane  well  supplied  with  blood 
vessels    and    nerves  that  can  pick   out   of  the  blood    certain 
material  to  form  secretions.     The  important  digestive  glands 
are  :  the  salivary,  the  gastric,  the  intestinal,  the  pancreas,  and 
the  liver. 

3.  The   mouth  is  the  first  organ    of  digestion.     Here  the 
foods  are  cut  and  ground  into  fine  particles,  mixed  with  saliva, 
and  pushed  into  the  pharynx.     In  the  mouth  are  the  teeth, 
the  tongue,  and  the  tonsils. 


94  HUMAN   PHYSIOLOGY  CHAP. 

4.  The  teeth  are  very  important  organs  of  digestion.    They 
are  made  of  dentine  covered  with  enamel  on  the  crown,  and 
cement  on  the  root.      They  are  filled  with  connective  tissue, 
blood  vessels,  and  nerves. 

5.  There  are  twenty  teeth  in  the  first  set  and  thirty- two  in 
the  second.     A  tooth  does  not  grow  after  it  is  once  fully  cut 
and  cannot  repair  itself;  hence  the  teeth  should  be  properly 
cared  for. 

6.  The   salivary  glands    pour  from  one  to  three  pints   of 
saliva  into  the  mouth  daily,  which  serves  to  keep  the  mouth 
moist,  to  dissolve  some  of  the  foods,  and  to  change  some  of 
the  starches  into  sugars. 

7.  Swallowing  is  accomplished  by  the  proper  action  of  a 
large  number  of  muscles.     The  food  passes  from  the  mouth 
through  the  pharynx  and  oesophagus  into  the  stomach. 

8.  The  stomach  is  the  greatest  enlargement  of  the  digestive 
canal  and  an  important  organ  of  proteid  digestion.     The  gas- 
tric juice  comes  from  the  innumerable  gastric  glands  and  con- 
tains an  acid  and  pepsin.    The  amount  of  gastric  juice  secreted 
daily  varies  from  ten  to  twenty  pints. 

9.  The  stomach  has  three  separate  layers  of  muscles,  which 
enable  it  to  contract  in  all  directions  and  to  thoroughly  churn 
the  food. 

10.  The  time  it  takes  to  digest  a  meal  depends  upon  the 
amount  and  kind  of  food  taken,  the  mode  of  cooking,  the  gen- 
eral health  of  the  person,  and  the  kind  and  amount  of  exercise 
taken.   The  food  remains  in  the  stomach  from  two  to  four  hours. 

11.  After   the    food    has    been    properly   changed   in   the 
stomach  it  passes  through  the  pylorus  into  the  small  intestine. 

12.  The  glands  of  the  intestines,  the  pancreas,  and  the  liver 
all  pour  secretions  into  the  intestines. 

13.  The  pancreatic  juice  is  the  most  important  digestive 
fluid,  for  it  can  do  all  that  the  other  juices  do,  and  besides  it 
changes  fats  and  oils  into  an  emulsion,  or  into  soap. 


vil  DIGESTION  95 

14.  The  intestinal  juice  is  secreted  in  very  small  quantities. 
It  aids  the  pancreatic  juice  in  acting  upon  starches  and  sugars. 

15.  The  bile  aids  the  pancreatic  juice  in  changing  the  fats. 
It  stimulates  the  walls  of  the   intestines  to  greater  muscular 
action  and  to  secretion. 

1 6.  In  the  mouth  starches  are  changed  into  sugars;  in  the 
stomach   proteids   are  dissolved ;    and  in  the  small    intestine 
starches  are  changed  into  sugars,  proteids  are  dissolved,  and 
fats  and  oils  are  changed  into  tiny  particles  so  that  they  can 
enter  the  blood. 

17.  The  bulk  of  the  contents  of  the  alimentary  canal  is 
greatest  in  the  small  intestine,  where  it  is  a  milklike  substance 
with  some  indigestible  solids  floating  in  it. 

1 8.  The  liquid  material  can  enter  the  blood,  but  the  solid 
is  a  waste  that  must  be  ejected  from   the  large   intestine  at 
regular  intervals. 


CHAPTER    VIII 

FROM   THE   ALIMENTARY    CANAL   TO   THE   HEART 

76.  Review.  —  We  have  now  learned  what  parts  the 
various  digestive  organs  play  in  the  preparation  of  foods 
for  the  blood.  We  have  seen  that  proteids,  carbohydrates, 
and  fats  are  the  only  foods  that  must  undergo  chemical 
changes  in  order  to  be  dissolved.  Water,  salt,  and 
oxygen  can  enter  the  blood  unchanged.  We  have 
learned  that  the  carbohydrates  are  changed  into  sugars, 
the  proteids  are  dissolved,  and  the  fats  and  oils  are 
broken  up  into  very  small  droplets  and  a  small 
amount  is  changed  to  soap.  We  have  seen  how  the 
oxygen  gets  through  the  walls  of  the  air  sacs  of  the 
lungs,  and  into  the  plasma  of  the  blood,  where  it  is 
picked  up  by  the  red  corpuscles. 

We  shall  learn  in  this  chapter  how  the  peptones, 
sugars,  fats,  salt,  and  water  get  through  the  walls  of  the 
body  and  into  the  blood.  You  will  remember  that  the 
alimentary  canal  is  a  tube  extending  through  the  body, 
and  anything  that  is  in  the  stomach  or  in  the  intes- 
tines is  in  the  alimentary  canal  but  really  not  in  the 
body.  The  digestive  tract  is  lined  with  a  delicate  mu- 
cous membrane  which  serves  as  a  sentinel  to  protect 
the  body  against  substances  that  are  not  dissolved  and  to 

96 


CH.VIII     FROM  THE  ALIMENTARY  CANAL  TO  THE  HEART    97 

pick  up  those  things  that  may  enter  the  blood.  There 
is  no  way  of  getting  from  the  alimentary  canal  into  the 
blood  except  by  passing  through  this  membrane. 

77.  Absorption.  —  Foods  in  the  form  of  a  liquid  can 
pass  through  the  mucous  membrane  in  any  part  of  the 
alimentary  canal,  through  the  delicate  walls  of  the  blood 
capillaries,  and  become  part  of  the  plasma.  The  word 
absorption  refers  to  this  soaking  through  the  walls,  but 
it  is  not  simply  a  soaking  process,  for  the  cells  are  active 
in  picking  up  the  little  particles  of  food  and  passing 
them  on  into  the  plasma  of  the  blood.  We  know  that 
the  sap  of  trees  goes  up  through  the  little  plant  cells  to 
the  leaves  by  passing  from  cell  to  cell  by  a  process 
called  osmosis.  Now,  in  a  similar  way,  the  foods  enter 
the  plasma.  We  may  say  that  absorption  is  in  part 
soaking  through  the  walls,  in  part  osmosis,  and  in 
part  due  to  the  action  of  the  living  cells  of  the  walls 
themselves. 

Foods  may  be  absorbed  all  along  the  alimentary  canal, 
but  there  are  some  places  where  absorption  occurs  more 
readily  than  at  others.  TJie  largest  amount  is  absorbed 
from  the  small  intestine.  Here  we  have  a  very  large 
surface  of  mucous  membrane  so  made  as  to  favor  rapid 
absorption  of  all  kinds  of  foods.  Next  in  importance 
is  the  large  intestine,  where  water  and  salt  are  absorbed 
chiefly.  Water,  salt,  some  sugars,  and  some  peptones 
may  be  absorbed  from  the  stomach,  but  the  amount  is 
comparatively  small.  A  very  little  water,  salt,  and  sugar 
may  enter  the  blood  from  the  mouth  and  even  from  the 
oesophagus. 

H 


98 


HUMAN   PHYSIOLOGY 


CHAP.  VIII 


78.  Absorption  of  Fats.  —  Although  fats  and  oils  are 
acted  upon  by  the  pancreatic  juice,  and  by  the  bile, 
which  together  break  them  up  into  very  small  drop- 
lets surrounded  by  a  thin  film  of  soap,  they  are  never 
really  dissolved  as  the  other  foods  are.  They  are  still 
butter,  lard,  tallow,  oils,  etc.  They  are  not  digested  but 
simply  emulsified.  In  the  intestines  a  small  amount  of 


FIG.  54.  —  Villi  of  the  small  intestine  (Zuppke)  :  A,  the  lacteal  at  rest ;  B,  the 
lacteal  filled  up  with  foods  ;  C,  the  muscles  contracting  and  forcing  the 
foods  out  into  the  lymphatic  vessels. 

soap  is  formed  to  aid  in  the  absorption  of  the  fats. 
Water  and  oil  will  not  mix.  Oil  of  any  kind  on  the 
hands  is  washed  off  with  difficulty  without  soap. 

Fats  and  oils  are  not  absorbed  with  the  other  foods; 
they  have  a  route  of  their  own.  The  mucous  membrane 
of  the  small  intestine  has  millions  of  little  projections 
called  villi  all  over  its  vast  surface.  A  villus  is  merely 
a  fold  of  the  mucous  membrane,  in  the  center  of  wJiicJi  is 


stomach  re 

¥. 


FIG.  55.  —  Showing  the  two  routes  of  foods  in  absorption  (Zuppke). 


ioo  HUMAN   PHYSIOLOGY  CHAP. 

a  small  duct  called  a  lacteal.  The  fats  and  oils  pass 
through  the  walls  of  the  villi  and  get  into  these  little 
lacteals ;  but  they  have  not  yet  reached  the  blood. 
The  lacteals  from  several  villi  unite  and  form  larger 
tubes,  known  as  lymphatic  vessels,  which  finally  empty 
into  a  single  trunk  about  the  size  of  a  goose  quill,  called 
the  thoracic  duct.  The  fats  together  with  a  small  amount 
of  the  other  foods  are  carried  up  through  the  thoracic  duct 
and  emptied  into  the  left  subclavian  vein  at  the  base  of 
the  neck.  Here  they  mingle  with  the  blood  and  are 
washed  along  to  the  right  side  of  the  heart. 

A  very  important  change  occurs  in  the  fats  in  absorp- 
tion, and  during  their  passage  through  the  lymphatics. 
There  are  little  swellings,  lyi)iph  nodes  or  glands,  on  the 
small  lymphatic  vessels,  in  which  the  fats  are  changed. 
The  butter,  lard,  suet,  goose  oil,  etc.,  that  we  eat  are 
here  changed  to  human  fat.  Every  animal  has  a  kind 
of  fat  peculiar  to  itself.  In  the  thoracic  duct  and  in 
the  blood  of  man  we  find  neither  lard  nor  tallow ;  they 
have  been  changed  to  human  fat  during  absorption. 

We  have  traced  the  fats  and  oils  into  the  blood  and  to 
the  right  side  of  the  heart.  Let  us  now  see  how  the 
other  foods  get  from  the  digestive  canal  to  the  right  side 
of  the  heart. 

79.  The  Other  Foods.  —  Peptones,  sugars,  salt,  and 
water  are  the  other  foods  that  we  left  in  the  intestines. 
These  pass  into  the  cells  of  the  mucous  membrane  and 
then  directly  into  the  blood  capillaries.  The  capillaries  of 
the  stomach  and  intestines  unite  to  form  many  veins,  all 
of  which  empty  into  the  portal  vein.  The  portal  vein  is 


vin       FROM  THE  ALIMENTARY  CANAL  TO  THE  HEART     101 

a  large  blood  vessel  that  gathers  up  the  blood  from  the 
stomach,  the  spleen,  and  the  intestines,  and  carries  it  to 
the  liver. 

Peptones  and  sugars  are  also  changed  during  absorp- 
tion. As  the  peptones  pass  through  the  cells  of  the 
mucous  membrane  they  are  changed  into  a  form  of  albu- 
min that  can  be  used  to  build  up  and  repair  the  cells  of 
the  body.  Sugars  are  also  changed  by  the  same  cells. 
Water  and  salt  are  not  changed.  In  the  portal  vein 
leading  to  the  liver  we  find  albumins,  sugars,  water, 
salt,  and  some  fats.  Before  these  foods  reach  the  heart 
they  must  pass  through  the  liver,  where  other  changes 
occur.  We  must  now  study  the  liver. 

80.  The  Liver.  —  The  location,  size,  color,  and  some 
of  the  uses  of  the  liver  we  learned  in  the  last  chapter. 
The  liver  is  made  up  of  five  lobes,  each  consisting  of 
many  lobules.  Each  lobule  receives  blood  from  a  small 
branch  of  the  portal  vein  and  from  the  hepatic  artery. 
The  lobules  consist  of  very  small  cells  that  do  many 
things  besides  manufacturing  bile. 

If  more  proteid  foods,  as  cheese,  eggs,  and  meats, 
are  eaten  than  the  body  needs,  they  are  changed  into 
sugars  or  fats  in  the  liver  cells.  The  albumins  cannot 
be  stored  up  in  the  body,  while  the  sugars  and  fats  can. 
All  of  the  sugar  that  is  not  needed  at  once  by  the 
cells  of  the  body  is  stored  up  in  the  liver  for  future  use. 
Fats,  water,  and  salt  are  not  changed.  The  liver  cells 
have  the  power  to  select  from  the  blood,  as  it  passes 
through  them,  certain  germs  and  poisons  that  some- 
times get  into  the  body  with  the  foods.  They  can  also 


102 


HUMAN   PHYSIOLOGY 


CHAP. 


destroy  harmful  substances  made  in  the  various  cells  of 
the  body.  So  we  see  that  the  liver  is  a  very  important 
organ,  for  it  does  many  things  to  keep  the  blood  pure 
and  to  keep  the  right  amount  of  the  different  foods  in 
the  blood. 


/ 


SHv 


FlG.  56.  —  Showing  two  lobules  of  the  liver.  (Modified  from  Schafer  by 
Zinns)  :  /,  portal  vein  bringing  blood  to  the  lobules;  HV,  beginning  of  he- 
patic vein  formed  by  the  union  of  the  capillaries  within  the  lobule;  SHV, 
hepatic  vein  carrying  blood  away  from  the  lobules. 

The  sugars  stored  up  in  the  liver  pass  into  the  blood 
whenever  the  body  needs  them,  and  they  reach  the 
heart  through  a  large  blood  vessel  called  the  ascending 
vena  cava. 

81.  Foods  in  the  Right  Heart.  —  The  fats  are  ab- 
sorbed by  way  of  the  lacteals  and  lymphatics,  or  by 
the  indirect  method,  and  all  the  other  foods  by  way  of 
the  blood  capillaries  and'  the  liver,  or  by  the  direct 
method.  The  two  again  unite  in  the  blood  in  the  right 
side  of  the  heart.  The  bread,  meat,  potatoes,  etc.,  that 
we  eat  are  changed  in  digestion,  so  that  they  get  into 


vni       FROM  THE  ALIMENTARY  CANAL  TO  THE  HEART     103 

the  body,  and  are  further  changed  in  absorption,  so  that 
they  can  be  used  to  nourish  the  cells  and  to  give  us 
strength.  The  proteids  are  now  albumins,  the  carbo- 
hydrates are  a  kind  of  sugar,  the  fats  and  oils  are 
human  fat,  and  the  water  and  salt  are  unchanged. 
The  plasma  of  the  blood  is  about  ninety  per  cent  water, 
and  dissolved  in  it  are  all  of  these  foods. 

82.  The  Large  Intestine. — We  have  learned  that 
the  food  reaches  its  largest  bulk  in  the  small  intestine 
because  the  quantity  absorbed  up  to  this  point  is  less 
than  that  of  the  digestive  fluids  added.  The  rapid 
absorption  of  all  kinds  of  foods  from  the  small  intes- 
tine, and  of  water  and  salt  from  the  large  intestine, 
diminishes  the  contents  very  much.  Toward  the  end  of 
the  colon  the  contents  become  quite  solid  in  consist- 
ency, and  take  on  a  darker  color. 

Many  kinds  of  bacteria  are  found  in  both  the  small 
and  large  intestines.  They  live  here  and  decompose 
many  of  the  undigested  food  materials.  But  they  do 
no  harm  if  the  large  intestine  is  emptied  every  day. 
In  this  way  many  useless  substances  taken  with  the 
foods  and  some  waste  products  formed  within  the  body 
are  removed. 

SUMMARY  OF  THE   MAIN   POINTS 

1.  Absorption  means  the  transfer  of  foods  from  the  alimen- 
tary canal  into  the  blood. 

2.  Foods  get  through  the   mucous  membrane  by  soaking 
through,  by  osmosis,  and  by  the  action  of  the  living  cells. 

,  3.    From  the  mouth  and  the  oesophagus  there  are  absorbed 
some  water  and  salt,  and  sometimes  small  amounts  of  sugar. 


104  HUMAN   PHYSIOLOGY  CHAP,  vm 

From  the  stomach  some  peptones  are  absorbed  in  addition  to 
the  above.  The  small  intestine  is  the  most  important  organ 
of  absorption,  for  from  it  fats  and  oils  are  absorbed  by  the  lac- 
teals,  and  peptones,  sugars,  water,  and  salt  by  the  capillaries. 
From  the  large  intestine  water  and  salt  are  absorbed. 

4.  In  the  cells  of  the  villi  and  in  the  lymph  nodes  of  the 
lymphatics  the  fats  are  changed  to  human  fats.     The  fats  pass 
up  through  the  thoracic  duct  and  enter  the  blood  in  the  left 
subclavian  vein  at  the  base  of  the  neck. 

5.  The  other  foods  enter  the  blood  capillaries  directly  and 
are  carried  into  the  portal  vein  which  leads  to  the  liver. 

6.  In  absorption  the  peptones  are  changed  to  albumins,  and 
the  sugars  are  also  changed  somewhat.     The  water  and  salt  are 
not  changed. 

7.  The  liver  may  change  the  albumin  not  needed  at  the 
time  into  fats  or  sugars  and  then  store  up  the  sugar  for  future 
use. 

8.  The  liver  destroys  certain  disease  germs,  removes  poisons, 
manufactures  bile,  serves  as  a  storehouse  for  sugars,  destroys 
worn-out  red  corpuscles,  and  oxidizes  certain  harmful  substances 
made  in  the  body. 

9.  The  fats  absorbed  by  the  indirect  route  and  the  other 
foods   by    the    direct   route    are    again   brought    together    in 
the  right  side  of  the  heart  and  form  the  nutritious  part  of  the 
plasma. 

10.  The  materials  that  cannot  be  absorbed  from  the  alimen- 
tary canal  accumulate  in  the  large  intestine  and  are  expelled 
at  regular  intervals. 


CHAPTER   IX 

HYGIENE   OF   DIGESTION   AND   ABSORPTION 

83.  Pure  Foods.  —  One  of  the  most  important  prob- 
lems for  us  to  consider  is  how  to  obtain  pure,  whole- 
some foods.  No  question  is  of  greater  moment  to 
health.  Foods  are  often  impure  because  they  contain 
disease  germs  and  dangerous  parasites.  It  is  well 
known  that  typhoid  fever,  cholera,  trichinosis,  and  nu- 
merous other  diseases  are  due  to  impure 'foods.  Meat 
from  diseased,  overheated,  wounded,  immature,  or  ema- 
ciated animals  is  very  dangerous,  and  should  not  be 
used  for  food.  Fruits  and  vegetables  unripe,  overripe, 
decayed,  or  stale  are  unwholesome,  and  should  never 
be  eaten.  Milk  from  cows  that  are  diseased,  or  that 
are  fed  on  "  swill  milk,"  "  distillery  slops,"  refuse  from 
vinegar  factories,  garbage,  and  other  unclean  or  unwhole- 
some foods,  or  that  are  kept  in  overcrowded,  unclean, 
or  otherwise  unhygienic  stables,  is  dangerous,  and 
should  not  be  used  for  food. 

Besides  being  unclean  and  containing  disease  germs, 
foods  are  often  impure  and  unwholesome  because  they 
have  been  adulterated  with  cheaper  and  less  nutritious 
substances.  Every  state  has  enacted  laws  which  make 
the  sale  of  adulterated  foods  an  offense  punishable  by  a 

105 


106  HUMAN   PHYSIOLOGY 


CHAP. 


fine  or  imprisonment.  Such  laws  are  wise  and  just,  and 
should  be  enforced  in  every  town  and  city.  Every  intel- 
ligent citizen  should  do  all  he  can  to  discourage  the  sale 
and  use  of  impure,  unwholesome,  or  adulterated  foods 
of  all  kinds. 

84.  Adulterated  Foods.  —  Milk  is  more  often  adulter- 
ated than  any  other  food.  The  watering  and  skimming 
of  milk  are  the  chief  ways  of  adulteration,  but  some- 
times a  substance  is  added  to  give  it  a  better  color. 
This  makes  the  milk  less  nutritious,  and  it  is  more 
likely  to  contain  disease  germs.  Milk  is  such  an  impor- 
tant food  in  every  household  that  the  utmost  efforts 
should  be  made  to  keep  it  pure  and  clean.  Butter  is 
sometimes  made  from  lard,  tallow,  and  cotton-seed  oil 
instead  of  from  rich  cream.  Such  imitations  are  called 
butterine  or  oleomargarine.  It  cannot  be  maintained 
that  butterine  is  unhealthful,  provided  it  is  made  of 
pure,  clean  materials,  but  it  is  very  often  sold  for 
good,  pure  butter.  Many  of  the  states  have  laws  re- 
quiring all  butterine  to  be  properly  labeled,  and  some 
require  a  conspicuous  sign  stating  the  fact  that  butter- 
ine is  there  sold  or  used.  Fats,  oils,  and  grease  are 
sometimes  used  in  the  manufacture  of  cheese,  but  any 
such  inferior  and  adulterated  product  put  on  the  mar- 
ket should  be  labeled  "imitation  cheese." 

Molasses,  sirup,  sugar,  honey,  etc.,  are  often  mixed 
with  glucose,  dextrose,  starch  sugar,  or  other  starchy 
preparations.  Candy  may  contain  glucose,  poisonous 
coloring  matter,  and  harmful  flavors.  Flour  and  bread, 
baking  powder,  saleratus,  fruit  jelly,  coffee,  chocolate, 


ix  HYGIENE  OF  DIGESTION  AND   ABSORPTION  107 

lard,  olive  oil,  vinegar,  liquors  and  wines,  drugs  and 
medicines,  and,  it  is  said,  in  Paris,  even  eggs,  are  among 
the  things  that  are  made  cheaper  and  less  wholesome 
by  various  processes  of  adulteration. 

85.  Cooking.  —  We  have  already  learned  some  reasons 
for  cooking  foods.  Let  us  now  see  the  relation  of  cook- 
ing to  digestion.  Nearly  all  foods,  both  vegetables  and 
meats,  are  softened  by  cooking  so  that  they  may  be  more 
easily  changed  by  the  digestive  juices  of  the  alimentary 
canal.  Proper  cooking  of  foods  is  really  a  kind  of  diges- 
tion, or  the  first  step  in  the  process  of  changing  foods 
into  blood.  Fats  are  an  exception.  Cooking  makes  fats 
more  difficult  to  digest,  since  they  are  changed  chemi- 
cally when  exposed  to  a  high  temperature  even  for  a 
short  time.  That  explains  why  potatoes,  eggs,  and 
meats  when  fried  are  less  digestible  than  when  cooked 
in  any  other  way.  Frying  is  the  least  wholesome  mode 
of  preparing  foods,  because  the  butter  used  permeates 
the  entire  mass  so  that  neither  the  saliva  nor  the  gastric 
juice  can  act  upon  the  foods  to  any  extent.  They  must 
go  undigested  until  they  reach  the  small  intestine,  where 
the  pancreatic  juice  acts  upon  them. 

Boiling  is  the  mode  of  cooking  generally  employed 
for  vegetables.  It  is  better  to  boil  than  to  fry  meats. 
Baking  and  roasting  come  next  in  importance,  but  broil- 
ing is  by  far  the  most  wholesome  way  of  preparing  meats. 
By  this  method  all  the  juices  of  the  meats  are  saved, 
the  high  heat  sealing  them  up  at  once. 

Scientific  cooking,  by  utilizing  foods  to  their  full 
extent  with  the  smallest  amount  of  waste,  will  do  much 


io8  HUMAN   PHYSIOLOGY  CHAP. 

to  cheapen  the  expense  of  living  and  to  contribute  to 
health  and  happiness  by  presenting  the  foods  in  a 
pleasing,  palatable,  and  digestible  form,  so  as  to  stimu- 
late the  appetite  and  aid  the  digestive  processes.  Cook- 
ing is  an  art  that  can  be  mastered  only  by  careful  study 
and  intelligent,  persistent  practice.  Every  young  woman 
should  regard  it  a  rare  accomplishment  to  be  able  to 
cook  and  serve  foods  so  that  they  will  be  of  the  greatest 
nutritive  value. 

86.  Care  of  Teeth. —  Most  persons  do  not  sufficiently 
realize  the  value  of  the  teeth  as  organs  of  digestion. 
It  is  a  fact  that  many  cases  of  indigestion  and  nervous- 
ness arise  from  insufficient  mastication  because  of  poor 
teeth.  Our  teeth  must  be  kept  in  condition  for  daily  use. 
A  tooth  that  has  a  cavity  should  be  filled  if  it  is  worth 
saving,  and  if  not,  it  should  be  removed.  If  several  teeth 
are  wanting,  they  should  be  replaced  by  artificial  teeth. 

Bacteria  are  the  chief  cause  of  bad  teeth.  Many 
harmless  bacteria  are  found  in  the  mouth,  but  others 
produce  poisonous  substances  that  cause  the  teeth  to 
decay.  Of  course  there  are  other  minor  causes  that 
tend  to  destroy  the  teeth,  as  taking  into  the  mouth  iron, 
acids,  etc.,  biting  too  hard  substances,  scratching,  or  in 
any  way  injuring  the  enamel. 

Particles  of  foods  lodge  between  the  teeth  and  unless 
removed  at  once  afford  excellent  food  material  for  bac- 
teria. These  little  organisms  attack  the  teeth  and  form 
cavities  in  them.  The  discolored  tartar  so  often  seen 
on  teeth  is  due  to  the  action  of  bacteria.  The  remedy 
is  difficult  and  expensive,  but  prevention  in  most  cases 


IX 


HYGIENE   OF  DIGESTION   AND   ABSORPTION 


109 


is  simple.  Knowing  the  cause  of  a  disease,  one  may  be 
able  to  prevent  it.  The  one  important  thing  is  to  keep 
the  teeth  free  from  food  materials  for  the  bacteria. 
How  can  this  be  done  ?  There  is  but  one  way.  The 
teeth  must  be  carefully  and  thoroughly  cleansed  after 
each  meal. 

</  N 

V*$//N 

°  !••••: f: 


\ 


m;^,   >*.  iw"A/K 

:!f^     '».        *     • -M         '       ^    ^. 


^ 


mm  •&*. 


FlG.  57.  —  Bacteria  commonly  found  in  the  mouth.     (Hopkins'  "Care  of  the 
Teeth."     D.  Appleton  &  Co.) 

We  should  early  form  the  habit  of  properly  caring 
for  the  teeth  daily.  A  good  cleansing  once  a  month 
will  not  take  the  place  of  the  daily  care  they  should 
receive.  The  particles  of  food  between  and  around  the 
teeth  should  be  removed  with  a  wood  or  quill  toothpick 
after  each  meal.  Food  between  teeth  that  are  close 
together  may  be  easily  removed  with  a  fine  silk  thread 
or  with  a  small  rubber  band.  A  soft  toothbrush  and 


I  io  HUMAN   PHYSIOLOGY  CHAP. 

lukewarm  water  should  be  used  at  least  twice  a  day,  or, 
still  better,  after  each  meal  and  just  before  going  to  bed 
at  night.  Besides,  it  may  be  well  to  clean  each  tooth 
occasionally  with  a  chisel-like  piece  of  hard  wood.  This 
gives  the  teeth  a  smooth  polish,  and  makes  it  easier  to 
clean  them  with  a  brush.  About  twice  a  year  they  should 
be  looked  over  by  a  dentist  and  repaired  if  they  need  it. 

87.  The  Appetite.  —  A  person  who  lives  as  he  should 
may  safely  trust  his  appetite  as  to  what  he  shall  eat. 
In  this  matter  the  lower  animals  have  no  trouble,  but 
man  is  always  concocting  something  new  to  give  greater 
variety  to  his  diet,  and  so  stimulate  his  natural  desire 
for  food.  This  leads  to  disturbances  of  various  sorts. 
How  many  things  that  a  person  dislikes  at  first  he  learns 
to  eat  by  repeated  attempts.  In  this  way  an  artificial 
appetite  may  be  created  for  any  new  thing  whether 
wholesome  or  injurious. 

The  condition  of  the  mind  and  nervous  system  has 
a  wonderful  influence  upon  the  appetite  as  well  as  upon 
digestion  and  nutrition.  A  cheerful  disposition  and  a 
joyous  nature  give  rise  to  good  digestion  and  more 
perfect  nutrition,  while  worry,  envy,  jealousy,  excite- 
ment, and  other  undesirable  states  of  mind  lead  to 
digestive  disturbances  that  make  good  health  an 
impossibility  even  when  a  person  takes  the  best  of 
care  of  himself.  A  pure-minded,  cheerful,  contented, 
industrious  person  is  likely  to  have  a  good  appetite  and 
good  digestion.  We  can  now  understand  the  phrase, 
"  laugh  and  grow  fat,"  and  see  why  a  change  of  scene 
and  a  long  vacation  are  often  the  best  of  medicines. 


ix  HYGIENE  OF  DIGESTION  AND   ABSORPTION  in 

Poor  digestion  frequently  comes  from  nervousness, 
when  the  stomach  is  not  diseased  at  all,  because  nerve 
strain,  from  whatever  source,  shows  itself  first  of  all  in 
disturbing  the  appetite  and  the  nutrition.  A  decayed 
tooth,  defective  eyes  and  ears,  and  even  an  irritating 
corn  on  a  toe  may  be  the  remote  cause  of  indigestion. 
If  the  true  cause  of  the  trouble  could  be  removed,  it 
would  not  be  necessary  to  make  any  changes  in  the 
diet 

88.  Hygiene  of  Eating.  —  What  a  person  eats  is  gen- 
erally determined  by  what  he  likes  and  can  get.  As  a 
rule  taste  is  a  safe  guide,  but  by  forming  bad  habits  of 
eating,  an  unnatural  craving  for  foods  neither  digestible 
nor  nutritious  may  result.  We  should  form  a  taste  for 
good,  wholesome  foods  that  agree  with  the  digestive 
organs  and  avoid  all  that  are  harmful  even  if  they  are 
palatable. 

Food  should  be  taken  at  the  same  hour  each  day 
and  at  regular  intervals  of  from  four  to  five  hours.  If 
this  is  done,  it  will  not  be  necessary  to  eat  between 
meals  and  so  deprive  the  stomach  and  the  glands  of  the 
rest  they  should  have.  Loss  of  appetite  and  indigestion 
are  often  caused  by  eating  at  all  hours.  It  is  a  good 
thing  to  rest  a  few  minutes  from  physical  and  mental 
work  just  before  taking  a  full  meal.  That  will  aid 
digestion  very  much.  Severe  exertion  immediately 
after  a  full  meal  is  equally  injurious  because  physical 
and  mental  exercise  drain  the  blood  away  from  the 
stomach  and  glands,  where  it  is  needed  to  properly 
digest  the  foods.  We  should  form  the  habit  of  eating 


ii2  HUMAN  PHYSIOLOGY  CHAP. 

three  good  meals  a  day  and  resting  a  few  minutes 
before  and  after  each  if  we  wish  to  be  well  and  strong. 

Another  important  caution  is  to  eat  slowly  and 
masticate  thoroughly.  It  is  essential  to  chew  the  foods 
thoroughly,  so  that  the  digestive  fluids  can  act  on  each 
particle.  Eating  slowly  gives  the  saliva  time  to  mix 
thoroughly  with  the  foods  in  the  mouth  and  to  change 
some  of  the  starches  into  sugars. 

Drinking  water  at  meals  does  little  harm  unless  the 
foods  are  washed  or  "  rafted  "  down  into  the  stomach. 
That,  of  course,  is  the  danger  to  be  avoided,  for  eating 
rapidly  and  washing  down  the  food  is  certain  to  cause 
indigestion.  Ice-cold  and  very  hot  foods  and  drinks 
should  be  avoided.  They  may  injure  the  teeth  by 
cracking  the  enamel,  and  the  stomach  by  delaying 
digestion  until  the  normal  temperature  can  be  restored. 

When  and  how  we  eat  and  drink  are  almost  entirely 
matters  of  personal  habit  which,  when  once  formed,  are 
difficult  to  change.  Happy  is  the  youth  who  forms 
habits  that  shall  be  his  friends  all  through  life.  He 
should  take  daily  a  sufficient  quantity  of  pure,  whole- 
some, plain  foods  selected  from  vegetables,  meats,  and 
fruits,  and  eat  at  the  same  hour  each  day  under  as  pleas- 
ant surroundings  as  possible.  It  is  not  necessary  to  have 
a  great  variety  at  any  meal,  but  it  is  important  to  have  the 
right  proportion  of  each  food  stuff.  Let  us  eat  to  live 
and  not  live  to  eat. 

89.  Dress  and  Digestion. — We  have  learned  in  the 
chapter  on  Respiration  that  the  postures  of  the  body 
and  the  mode  of  dressing  the  chest  are  of  great 


ix  HYGIENE  OF  DIGESTION  AND  ABSORPTION  113 

importance  to  proper  breathing  and  good  health.  What 
was  said  there  applies  also  to  digestion.  A  lounging, 
careless  position  in  sitting  and  standing  tends  to  displace 
the  abdominal  organs.  Tight  lacing  about  the  waist 
depresses  the  stomach,  intestines,  kidneys,  and  liver, 
weakens  the  muscles  of  the  abdomen,  interferes  with 
abdominal  breathing,  and  deranges  the  organs  situ- 
ated in  the  pelvic  cavity.  These  organs  thus  crowded 
downward  day  after  day  soon  become  permanently 
fixed  in  these  abnormal  positions.  See  Figure  32  on 
page  67. 

We  are  told  by  physicians  that  the  displacement  of  the 
abdominal  and  pelvic  organs  is  the  cause  of  constipa- 
tion, biliousness,  headache,  backache,  general  weakness, 
and  many  other  ailments" of  a  more  serious  nature. 
All  the  difficulties,  suffering,  peevishness,  and  petulance 
due  to  these  disorders  may  be  avoided  if  we  form  cor- 
rect habits  of  standing,  sitting,  and  lying,  and  wear 
clothing  fitting  loosely  about  the  chest  and  waist. 

All  garments  of  men,  women,  and  children  should  be 
suspended  from  the  shoulders  and  not  from  a  belt  worn 
about  the  waist.  They  should  be  loose  enough  to  per- 
mit the  utmost  freedom  for  enlarging  the  chest  in 
breathing  and  for  the  natural  functioning  of  the 
abdominal  and  pelvic  organs.  The  conventional  dress 
of  women  is  particularly  faulty  in  this  matter,  and  in- 
telligent arid  cultured  women  should  do  their  utmost 
to  institute  a  crusade  against  this  unhygienic  practice 
so  fashionable  at  present.  It  has  been  well  said  that 
fashion  makes  cowards  of  us  all. 


ii4  HUMAN   PHYSIOLOGY  CHAP. 

90.  Diseases  of  the  Alimentary  Canal.  —  We  have  seen 
that  many  disease  germs  enter  the  body  with  the  air 
we  breathe  and  cause  certain  diseases  of  the  air  pas- 
sages. The  alimentary  canal  is  another  important 
channel  through  which  thousands  of  bacteria  get  into 
the  body  daily.  The  germs  of  typhoid  fever,  dysentery, 
and  cholera  can  get  into  the  body  only  by  this  means, 
while  those  of  consumption,  diphtheria,  and  scarlet 


FIG.  58.  — Bacteria  of  typhoid  fever  (Pratt). 

fever  may  enter  the  body  either  with  the  air  or  with 
the  foods.  These  diseases  will  be  discussed  in  a  later 
chapter. 

Among  the  other  important  ailments  of  the  diges- 
tive tract  are  dyspepsia,  intestinal  indigestion,  liver 
trouble,  and  appendicitis.  Dyspepsia  is  a  disease  of  the 
stomach  and  may  be  due  to  a  great  variety  of  causes, 
but  the  most  common  are  coarse,  indigestible,  poorly 
cooked  articles  of  food,  rapid  eating,  bad  teeth,  insuf- 
ficient mastication,  lack  of  variety  in  diet,  and  excessive 
use  of  alcoholic  beverages.  If  our  foods  are  plain  and 
wholesome,  varied  more  or  less  from  day  to  day,  prop- 
erly cooked,  eaten  slowly,  well  masticated,  and  the  amount 
taken  not  too  large,  the  stomach  will  do  its  work  well. 


IX 


HYGIENE   OF   DIGESTION   AND   ABSORPTION 


The  foods  remain  in  the  small  intestine  for  about 
twelve  hours  and  undergo  very  important  chemical 
changes.  If  the  foods  have  not  been  properly  prepared 
for  the  action  of  the  intestinal  fluids,  neither  digestion 
nor  absorption  is  carried  on  as  it  should  be,  and 
the  foods  will  not  serve  their  purpose.  The  causes  of 
dyspepsia,  together  with  insufficient  clothing  to  keep  the 
abdomen  warm,  and  neglect  to  empty  the  large  intestine 
at  least  once  a  day,  are  among  the  most  frequent  causes 
of  intestinal  indigestion.  Mental  and  physical  over- 
work always  derange  the  stomach  and  the  intestines. 

If,  for  any  reason,  the  functions  of  the  liver  are 
impaired,  digestion  and  absorption  will  be'  disturbed, 
and  all  the  tissues  of  the 
body  will  suffer.  The  causes 
of  jaundice  and  other  liver 
troubles  are  numerous  and 
of  a  rather  complicated  na- 
ture, but  by  keeping  the 
body  in  good  health  it  is  not 
likely  that  ..this  organ  will 
become  diseased.  Unwhole- 
some foods,  alcoholic  bever- 
ages, and  constipation  are 
generally  connected  with 
liver  troubles. 

At  the  lower  end  of  the  caecum  there  is  a  small  organ 
about  two  and  one  half  inches  long  known  as  the  vermi- 
form appendix.  As  far  as  known  it  serves  no  purpose 
in  man.  It  is  a  dangerous  little  organ  because  it  is  the 


SffAe. 


FIG.  59.  —  Showing  the  appendix. 
(Drawn  by  Mater.) 


n6  HUMAN   PHYSIOLOGY  CHAP. 

seat  of  the  disease  known  as  appendicitis.  The  cause  of 
this  disease,  which  is  quite  common,  is  unknown  at 
present.  It  was  once  thought  that  grape  seeds  and 
other  small,  hard  substances  taken  into  the  stomach 
might  lodge  in  the  appendix  and  give  rise  to  an  in- 
flammation, and  so  cause  appendicitis.  But  such  sub- 
stances rarely  cause  the  disease. 

91.  Alcohol  and  Digestion.  —  The  delicate  mucous 
lining  of  the  alimentary  canal  is  greatly  irritated 
by  coming  in  contact  with  alcohol.  There  are  two 
organs  of  digestion  which  seem  to  be  especially  vul- 
nerable to  the  attacks  of  alcohol.  The  first  of  these 
is  the  stomach.  The  blood  capillaries  of  the  stomach 
enlarge,  causing  a  congestion  of  the  mucous  membrane. 
The  glands  secrete  an  excessive  amount  of  gastric  juice 
when  thus  stimulated.  In  time  the  gastric  juice  be- 
comes diminished  both  in  quantity  and  in  digestive 
power.  The  stomach  will  not  respond  to  an  ordinary 
natural  stimulus  if  alcoholic  beverages  are  habitually 
used.  This  leads  to  a  loss  of  appetite  and  dyspepsia. 

The  second  organ  to  be  seriously  affected  by  alco- 
holic beverages  is  the  liver.  You  will  remember  that 
the  foods  which  enter  the  capillaries  of  the  stomach 
are  carried  directly  into  the  portal  vein  and  to  the  liver. 
All  of  the  alcohol  absorbed  from  the  stomach  must  go 
straight  to  this  organ.  The  liver  capillaries  become 
enlarged  with  blood,  and  the  cells  cannot  do  their  work 
as  they  should.  This  first  enlargement  may  be  fol- 
lowed in  time  by  fatty  decay  of  the  liver  substance, 
which  causes  an  abnormal  increase  in  size,  or  by  a 


ix  HYGIENE   OF   DIGESTION   AND   ABSORPTION  117 

shriveling  of  the  true  liver  substance  which  causes  the 
peculiar  nodules  that  give  it  the  name  "  hob-nailed " 
or  "  gin-drinker's  "  liver.  Either  of  these  conditions 
unfits  the  liver  to  perform  its  numerous  duties. 

92.  The  Large  Intestine.  —  By  a  little  effort  the  large 
intestine  may  be  trained  to  empty  itself  every  morning. 
This  is  a  very  important  matter,  for,  if  the  useless  and 
harmful  substances  are  retained  too  long,  they  weaken 
the  intestines,  impair  digestion  and  absorption,  cause 
diseases  of  the  liver,  and  lead  to  various  other  disorders. 
Loss  of  appetite,  drowsiness,  headache,  biliousness,  and 
constipation  are  among  the  symptoms  that  result  from 
neglect  of  this  very  important  personal  matter. 

SUMMARY   OF  THE   MAIN   POINTS 

T.  Many  foods  contain  disease  germs  and  hence  are  danger- 
ous to  eat.  Milk,  water,  meats,  vegetables,  and  fruits  must  be 
cared  for  properly  after  they  are  brought  to  the  house. 

2.  Typhoid    fever,  cholera,  dysentery,   and   trichinosis   are 
often  due  to  impure  or  spoiled  foods. 

3.  Foods  are  sometimes  made  impure  by  adulteration  with 
cheaper  and  less  nutritious  substances.     Milk,  butter,  cheese, 
molasses,   jelly,   sirup,  sugar,  tea,  honey,  candy,  flour,    bread, 
baking  powder,  saleratus,  coffee,  chocolate,  lard,  olive  oil,  vine- 
gar, liquors  and  wines,  drugs   and  medicines,  are  among  the 
things  that  are  adulterated. 

4.  Cooking  is  the  first  step   in   the    process  of  digestion. 
Boiling,  roasting,  baking,  stewing,  broiling,  and  frying  are  com- 
mon modes  of  preparing  foods. 

5.  Teeth  must  be  kept  clean  and  free  from  particles  of  food. 
They  should  be  cleaned  with  a  brush  and  tepid  water  at  least 
twice  a  day. 


n8  HUMAN  PHYSIOLOGY  CHAP,  ix 

6.  Avoid  extremes  of  temperature  in  foods,  and  hard,  metal- 
lic toothpicks,  as  they  tend  to  injure  the  enamel. 

7.  A  natural  appetite  is  a  safe  guide  to  follow  in  the  selec- 
tion of  foods,  but  the  appetite  may  easily  become  perverted. 

8.  A  cheerful  disposition  and  a  joyous  nature  give  rise  to 
good  digestion  and  perfect  nutrition ;  while  worry,  envy,  jeal- 
ousy, etc.,  lead  to  digestive  disturbances  that  make  good  health 
and  happiness  impossible. 

9.  Foods  should  be  eaten  at  regular  intervals  of  several 
hours,  so  that  the  digestive  organs  may  have  their  needed  rest. 
Rest  of  a  few  minutes  before  and  after  full  meals  is  a  great  aid 
to  digestion. 

10.  Eat   slowly,  masticate  well,  drink    little .  at   meals,  be 
cheerful  and  happy,  and  select  plain,  wholesome  foods  that  are 
well  cooked,  if  you  wish  to  be  well  and  strong. 

11.  Dress  about  the  waist  should  fit  loosely,  so  as  not  to  push 
out  of  place  the  abdominal  and  pelvic  organs.     All  garments 
should  be  suspended  from  the  shoulders  and  not  from  a  belt 
worn  about  the  waist. 

12.  Dyspepsia,  intestinal  indigestion,  and  liver  troubles  are 
among  the  common   diseases  of  the  digestive  organs.     They 
come  from  unhygienic  habits  of  eating,  drinking,  and  living. 

13.  Alcohol  has  a  specific  effect  upon  the  stomach,  intes- 
tines, and  liver ;  it  tends  to  impair  their  functions  permanently 
if  used  habitually. 

14.  The  large  intestine  should  be  trained  to  empty  itself 
every  morning. 


CHAPTER   X 

CIRCULATION   OF   THE  BLOOD 

93.  Review.  —  We  have  learned  that  the  human  body 
is  made  up  of  millions  upon  millions  of  very  tiny  cells, 
each  of  which  must  have  food  and  oxygen.  The  cells 
derive  their  nourishment  from  the  blood  as  it  circulates 
through  the  various  tissues.  Oxygen  from  the  air, 
water,  and  solid  foods  changed  and  dissolved  by  the 
digestive  fluids,  all  get  into  the  blood  and  form  the  part 
which  the  cells  need  to  nourish  them. 

The  cells  cannot  move  about  in  search  of  food,  and 
so  blood  must  be  carried  to  every  organ  and  tissue  of 
the  body.  The  amoeba,  you  remember,  is  a  single  cell 
and  has  the  power  to  move  about  freely  in  the  water 
from  which  it  can  obtain  its  food.  But  all  higher  ani- 
mals, and  plants,  as  well,  have  a  fluid  of  some  kind 
circulating  within  them  for  the  purpose  of  carrying 
food  materials  to  each  and  every  cell  and  removing 
waste  substances  and  worn-out  parts.  In  the  tree  the 
sap  forms  this  circulating  medium,  and  in  animals  it  is 
the  blood. 

Neither  plants  nor  animals  can  live  without  such  a 
circulating  medium,  which  is  truly  a  "  river  of  life," 
carrying  to  every  cell  life-giving  material,  and  remov- 

119 


CHAP,  x  CIRCULATION  OF  THE   BLOOD  121 

ing  from  every  cell  the  substances  which  would  cause 
disease  and  death. 

94.  The  Heart.  —  In  studying  absorption  we  learned 
that  the  foods  taken  into  the  blood  from  the  alimentary 
canal  both  by  the  direct  and  the  indirect  methods  are 
brought  together  in  the  right  side  of  the  heart. 

The  heart  is  about  the  size  of  a  person's  clenched  fist 
In  an  adult  it  is  about  five  inches  long  and  three  and 


FIG.  61.  —  The  lungs,  heart,  and  large  blood  vessels,  front  view  (Zuppke). 

one  half  inches  thick,  and  weighs  about  ten  ounces.  It 
is  situated  at  the  center  of  the  chest  between  the  lungs, 
with  its  apex  inclined  to  the  left  and  front.  For  this 
reason  you  can  feel  the  heart  beat  best  if  you  place 
your  hand  over  the  left  side  of  the  chest  on  a  level 
with  the  lower  part  of  the  breastbone.  The  heart  has 
a  saclike  covering,  resembling  the  pleura  of  the  lungs, 
folded  around  it ;  this  is  the  pericardium.  There  is  a 
small  amount  of  fluid  in  this  sac,  which  serves  to  oil 


122 


HUMAN   PHYSIOLOGY 


CHAP. 


Carot/of 
Arteries 


Pu/monary 
'Artery 
ertAt/r/c/e 


the  surfaces  and  enables  the  heart  to  work  with  very 
little  friction. 

The  heart  is  a  hollow,  muscular  organ  divided  into 
two  separate  parts,  the  right  and  left  sides,  by  a  strong 

partition  which  extends 
from  the  base  above  to 
the  apex  below.  Each 
side  consists  of  two 
chambers  with  an  open- 
ing between  them.  The 
upper  is  called  the  auri- 
cle, and  the  lower  the 
ventricle.  The  muscular 
walls  of  the  ventricles 
are  much  thicker  and 
stronger  than  those  of 
the  auricles,  and  those 
of  the  left  ventricle  are 
nearly  three  times  as 
thick  as  those  of  the 
right.  The  reason  for 
this  difference  will  ap- 
pear when  the  functions  of  these  chambers  are  described. 

Get  a  sheep's  heart  from  your  butcher  and  observe  especially 
the  four  chambers,  the  thickness  of  the  walls,  the  valves,  and  the 
openings. 

95.  Valves  and  Openings  of  the  Heart. — The  right 
auricle  has  several  openings  through  which  the  blood, 
returned  from  all  parts  of  the  body,  enters.  The  right 
ventricle  has  one  opening  by  which  the  blood  enters 


FIG.  62.  —  The  heart  and  large  blood 
vessels,  front  view  (Zuppke). 


CIRCULATION   OF  THE   BLOOD 


123 


from  the  right  auricle,  and  one  by  which  the  blood  leaves 
it  through  the  pulmonary  arteries  and  goes  to  the  lungs. 
The  left  auricle  has  four  openings  through  which  the 


•n 


FlG.  63.  —  Interior  of  the  right  auricle  and  ventricle.  (Thornton's  "Human 
Physiology"):  i,  descending  vena  cava;  2,  ascending  vena  cava  ;  3,  right 
auricle;  4,  semilunar  valves;  5,  5',  5",  tricuspid  valve;  6,  pulmonary 
artery;  7,  arch  of  aorta;  8,  aorta;  9,  large  branches  of  the  aorta;  10,  left 
auricle  ;  n,  left  ventricle. 

blood,  returning   from  the  lungs,  enters.     In  the  left 
ventricle  there   are   two   openings;    one    between   the 


124 


HUMAN   PHYSIOLOGY 


CHAP.  X 


auricle  and  ventricle,  and  one  through  which  the  blood 
escapes  into  the  aorta. 

These  openings  are  all  guarded  by  gateways,  or  folds 
of  the  thin  lining  membrane  of  the  heart,  called  valves. 
All  the  valves  open  one  way  only,  and  so  permit  the 
blood  to  flow  in  one  direction,  but  prevent  its  return. 
Guarding  the  opening  between  the  right  auricle  and 
ventricle  is  a  large,  three-pointed  valve  called  the 
tricuspid.  The  one  in  the  left  side  is  a  two-pointed 

valve  called  the 
mitral  because 
it  looks  like  a 
bishop's  cap. 
The  valves  be- 
tween the  ven- 
tricles and  the 
arteries  are 
called  the  semi- 
lunar  valves  from  their  half-moon  shape.  Sometimes 
the  valves  of  the  heart  do  not  work  as  they  should,  and 
the  person  suffers  from  valvular  heart  disease. 

96.  Blood  Vessels. — The  arteries  are  the  vessels  that 
convey  blood  from  the  ventricles  to  all  parts  of  the 
body.  They  always  lead  from  the  heart.  The  arteries 
have  thick,  strong,  tough  walls  made  of  muscles,  elastic 
tissue,  and  a  lining  of  very  thin,  smooth  membrane. 
The  muscles  enable  the  arteries  to  enlarge  whenever 
more  blood  is  needed  in  any  part  of  the  body  and  to 
contract  when  a  smaller  amount  is  required.  There  are 
nerves  which  regulate  the  size  of  the  arteries,  causing 


FIG.  64.  — Aorta  cut  open,  showing  semilunar  valves 
(Zuppke). 


FIG.  65.  —  Showing  the  plan  of  the  circulation  (Zuppke) . 


i26  HUMAN   PHYSIOLOGY  CHAP. 

them   to  dilate  or  contract  as  the  supply  of   blood   in 
different  organs  may  require. 

The  arteries  divide  and  subdivide  until  they  are  very 
small  and  finally  end  in  capillaries,  which  are  the  small- 
est blood  vessels  of  the  body.  The  capillaries  permeate 
every  part  of  the  body.  You  cannot  prick  yourself 
with  a  needle  without  rupturing  some  of  these  little 
tubes.  The  walls  of  the  capillaries  are  very  thin,  con- 


FIG.  66.  —  Showing  the  relation  of  the  capillaries  to  an  artery  and  a  vein 
(Zinns). 

sisting  of  a  single  layer  of  flattened,  elongated  cells  held 
together  by  a  small  amount  of  cementing  material. 
They  are  such  small  vessels  that  the  corpuscles  must 
pass  through  one  by  one,  and  so  arranged  as  to  be  able 
to  carry  blood  to  each  and  every  living  cell  of  the  body. 
It  is  from  the  capillaries  that  some  of  the  blood  escapes 
through  the  thin  walls  and  comes  in  contact  with  the 
cells. 

Although  the  capillaries  are  numerous  in  all  parts  of 
the  body,  they  are  exceedingly  short,  being  only  a  small 


CIRCULATION   OF  THE   BLOOD 


127 


fraction  of  an  inch  in  length.  They  combine  and  form 
larger  vessels  known  as  veins.  In  all  parts  of  the  body 
may  be  found  small  veins  which  unite  to  form  larger 
and  still  larger  ones,  until  there  are  only  two  great 
trunks,  the  ascending  and  descending  vena  caves,  that 
empty  into  the  right  auricle.  The  function  of  the  veins 
is  to  return  the  blood  from  the  capillaries  to  the  heart. 
The  veins  differ  from  the  arteries  in  that  their  walls  are 


M 

I 


FIG.  67. —  Showing  valves  in  veins  (Zuppke). 

lighter  and  less  elastic,  and  in  that  they  are  provided  with 
valves  which  do  not  obstruct  the  flow  of  blood  toward 
the  heart  but  prevent  its  return  to  the  cells.  They  lie 
nearer  the  surface  of  the  body  than  the  arteries  and 
form  the  purple-looking  streaks  which  we  frequently 
see  on  the  hands  and  arms  of  a  thin  person.  Blood 
containing  considerable  oxygen  is  brig/it  red  in  color;  but 
as  it  returns  from  the  cells,  where  it  has  exchanged  most 
of  its  oxygen  for  carbon  dioxid  and  other  waste 
materials,  it  is  very  dark  red.  The  purple  color  is  due  to 


128 


HUMAN    PHYSIOLOGY 


CHAP. 


the  fact  that  very  dark  red  blood  is  seen  through  the 
yellowish  skin.  The  blood  escaping  from  a  cut  vein 
looks  bright  red  because  the  moment  it  comes  in  con- 
tact with  air  it  takes  up  oxygen  which  changes  its 
color  at  once. 

97.  Lymphatics.  —  Some  of  the  blood  that  exudes 
from  the  capillaries  and  forms  part  of  the  lymph  around 
the  cells  does  not  again  enter  the  capil- 
laries but  is  returned  to  the  blood  by 
means  of  the  lymphatics.  We  studied 
lacteals  and  lymphatics  in  connection 
with  absorption  of  fats  from  the  small 
intestine.  The  spaces  between  the  cells 
in  all  parts  of  the  body  are  filled  with 
lymph  from  which  the  cells  get  their 
foods  and  to  which  they  give  off  their 
wastes.  In  these  lymph  spaces  the 
lymphatic  capillaries  have  their  begin- 
ning. They  serve  to  return  most  of  the 
cell  wastes  into  the  blood,  carbon  dioxid 
being  the  only  waste  that  enters  the  capil- 
laries and  is  returned  through,  the  veins. 
The  lymphatics  resemble  the  veins  in 
their  structure,  but  they  are  much 
smaller,  have  thinner  walls,  and  have 
valves  closer  together. 
The  lymphatics  may  be  said  to  begin  in  lymph  spaces 
in  all  parts  of  the  body.  Uniting,  they  gradually  grow 
larger  until  they  form  two  main  ducts  which  empty 
into  the  veins  at  the  base  of  the  neck.  The  left  thoracic 


F  [G.  68.  —  Lymphat- 
ics of  the  right 
arm.  G,  lymph 
glands  (Huxley). 


CIRCULATION   OF  THE  BLOOD 


129 


duct  returns  the  lymph  from  the  entire  body  below  the 

diaphragm,  from  the  left  arm,  and  from  the  left  half  of 

the  chest,   head,  and  face.     It  empties   into   the    sub- 

clavian  vein  of  the  left  arm.     The  right  lymphatic  duct 

is  much  smaller,  returning  the  lymph 

from  the  right  arm  and  from  the  right 

side  of  the  chest,  head,  and  face.     It 

empties  into  the  right  subclavian  vein. 

The     lymph    passes    through    lymph 

nodes  found  along  the  course  of  the 

lymphatic  vessels.    In  these  the  lymph 

may  undergo  certain  changes,  and  so 

become  fitted  for  use  in  other  parts  of 

the  body. 

The  lymphatic  vessels  are  very  im-  FlGbo^y ~ 
portant.  When  they  work  properly  all 
of  the  wastes  produced  by  the  cells  are 
drained  off  into  the  blood  and  not  per- 
mitted to  stagnate  in  the  lymph  spaces. 
In  this  way  the  cells  have  new  and  fresh  foods  carried 
to  them  as  they  need  it,  and  the  wastes  removed  as  fast 
as  they  are  produced.  Sometimes  they  do  not  work  as 
they  should,  and  the  lymph  accumulates  in  the  spaces 
around  the  cells,  causing  a  disease  known  as  dropsy. 

The  proper  work  of  the  lymphatics  depends  to  a 
large  extent  upon  physical  exercise.  Muscular  move- 
ment serves  as  a  natural  massage  for  the  lymphatics, 
and  pushes  the  lymph  onward  toward  the  heart.  A 
sufficient  amount  of  -healthful  exercise  makes  one  feel 
better,  even  in  hot  weather,  because,  when  the  lymph  is 


drained  by 
each  lymph  trunk. 
(Buchholz)  :  /4,the 
left  thoracic  duct ; 
Bt  the  right  lymph 
trunk. 


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CHAP.  X  CIRCULATION  OF  THE  BLOOD  131 

properly  returned  into  the  blood,  poisonous  waste  mate- 
rials are  at  once  removed  and  so  cannot  interfere  with 
the  free  and  natural  action  of  the  cells.  Exercise  opens 
all  the  drainage  tubes  and  renovates  the  entire  organism. 

98.  Course  of  the  Blood.  —  We  saw  that  the  as ce tid- 
ing vena  cava  returns  the  blood  from  the  lower  extrem- 
ities, the  pelvic  and  abdominal  organs,  in  fact,  from  the 
entire  body  below  the  level  of  the  heart ;  and  the  de- 
scending vena  cava  returns  the  blood  from  the  head, 
arms,  and  chest,  or  from  the  body  above  the  level  of 
the  heart.  These  two  trunks  empty  into  the  right 
auricle.  As  soon  as  the  right  auricle  is  full  its  muscular 
walls  begin  to  contract.  The  blood  cannot  return  into 
the  large  veins  but  must  flow  into  the  right  ventricle. 
When  that  chamber  is  filled  it  begins  to  contract.  Then 
the  tricuspid  valve  closes  and  prevents  the  blood  from 
returning  into  the  auricle.  The  only  opening  left  is  the 
one  into  the  pulmonary  arteries  which  carry  the  blood 
to  the  lungs. 

You  remember  how  the  dark  blood  that  comes  to  the 
capillaries  of  the  lungs  is  exposed  to  the  oxygen  of  the 
air  sacs.  Here  the  blood  loses  carbon  dioxid,  organic 
impurities,  etc.,  and  gains  a  very  large  amount  of 
oxygen.  In  this  way  the  blood  is  said  to  be  purified. 
The  dark  red,  almost  black,  blood  becomes  bright  red 
or  scarlet.  It  is  now  sent  back  through  the  pulmonary 
veins  to  the  left  auricle. 

The  blood  passes  the  mitral  valve  and  goes  into  the 
left  ventricle.  When  that  chamber  is  full,  the  blood  is 
forced  out  into  the  aorta.  The  mitral  valve  closing  pre- 


132 


HUMAN   PHYSIOLOGY 


CHAP. 


vents  the  reflow  of  the  blood  into  the  auricle.  The  aorta 
is  the  largest  artery  of  the  body.  It  gives  off  branches 
that  go  to  the  head  and  arms,  and  then  it  bends  down 
and  gives  off  branches  to  muscles,  to  the  stomach,  the 
liver,  the  spleen,  the  kidneys,  and  to  the  intestines. 
In  the  lower  part  of  the  abdomen  it  divides  into  two 


Descewtfa 


FIG.  71. —  Showing  the  course  of  blood  through  the  heart  (Zuppke). 

large  branches  called  the  right  and  left  common  iliac 
arteries.  The  largest  branch  of  each  of  these  is  called 
the  external  iliac,  and  farther  down  it  is  called  the 
femoral,  which  carries  the  blood  to  the  leg  and  foot. 

The  arteries  continue  to  divide  until  the  vessels  are 
smaller  than  the  finest  hair.  The  blood  is  now  in  the 
capillaries,  from  which  some  of  it  exudes  to  become  part 


x  CIRCULATION   OF  THE   BLOOD  133 

of  the  lymph  around  the  cells.  The  capillaries  unite  to 
form  the  small  veins.  The  blood  then  continues  to  flow 
on  in  larger  and  larger  veins  until  it  returns  to  the  right 
auricle.  Then  it  goes  to  the  lungs  as  before  and  back 
to  the  left  heart.  In  this  way  it  keeps  on  circulating 
day  and  night,  from  birth  till  death.  A  study  of  figures 
60  and  70  will  show  the  course  of  the  blood  through 
the  larger  vessels. 

Let  us  trace  the  blood  from  the  right  auricle  to  the 
stomach  and  back  again  :  right  auricle,  tricuspid  valve, 
right  ventricle,  semilunar  valve,  pulmonary  arteries, 
capillaries  of  the  lungs,  pulmonary  veins,  left  auricle, 
mitral  valve,  left  ventricle,  semilunar  valve,  aorta,  arch 
of  aorta,  thoracic  aorta,  abdominal  aorta,  gastric  artery, 
capillaries  of  the  stomach,  gastric  vein,  portal  vein, 
capillaries  of  liver,  hepatic  vein,  ascending  vena  cava, 
right  auricle.  In  the  same  way  blood  may  be  traced  to 
any  part  of  the  body. 

99.  Rate  of  Blood  Flow.  —  The  blood  does  not  flow 
at  a  uniform  rate  in  all  parts  of  its  course.  We  know 
that  water  in  a  stream  flows  most  rapidly  where  the 
bed  is  narrowest,  and  for  the  same  reason  the  blood 
flow  is  most  rapid  in  the  aorta  and  diminishes  in  rate 
throughout  the  arteries.  In  the  capillaries  it  moves 
very  slowly.  For,  although  the  capillaries  are  very 
small,  they  are  so  numerous  that  their  combined  area 
is  many  times  that  of  the  aorta.  In  the  veins  the  blood 
flows  faster  again  and  increases  in  rate  toward  the  heart. 
Figure  72  indicates  the  combined  area  of  the  blood 
vessels  in  different  parts  of  the  system.  The  rate  of 


134 


HUMAN   PHYSIOLOGY 


CHAP. 


^ 
Aorta 


-1  y&tae 


flow  is  so  great  that  the  blood  makes  one  circulation 
from  the  heart  to  the  tissues  and  back  to  the  heart 

in  about  twenty-two 
seconds.  It  takes 
the  blood  longer  to 
go  to  the  toes  and 
fingers  than  to  parts 
of  the  body  nearer 

FIG.  72.  — Showing  how  the  blood  vessels  com-      the    heart.       The    eil- 
pare  in  area  (Zuppke).  ,  •  ,  • ,        /-  /  /       / 

tire  quantity  of  blood 
passes  through  the  heart  about  three  times  per  minute. 

100.  What  makes  the  Blood  Move?  — There  are  a 
number  of  different  causes  which  together  keep  the 
blood  in  constant  motion.  The  most  important  cause 
is  the  contraction  of  the  muscles  of  the  heart.  When 
the  strong,  thick  muscles  of  the  left  ventricle  contract, 
the  blood  is  pushed  into  the  aorta  with  great  force. 
The  continued  pumping  of  the  heart  keeps  forcing 
more  and  more  blood  into  the  aorta  and  thus  pushing 
it  along  through  all  the  blood  vessels.  The  elastic 
walls  of  the  arteries  aid  the  heart  very  much  in  forcing 
the  blood  along. 

The  heart  works  like  an  automatic  pump.  There 
are  two  nerves  going  to  the  heart  which  control  and 
regulate  its  activity.  One  of  these  stimulates  the 
muscles  of  the  heart  and  makes  them  work  faster,  as 
when  we  are  running  hard ;  the  other  checks  the  mus- 
cular action  and  makes  the  heart  beat  slower.  These 
two  nerves  act  like  the  governor  of  an  engine. 
They  determine  the  rate  of  the  heart  beat,  and  so  the 


x  CIRCULATION  OF  THE   BLOOD  135 

amount  of  blood  that  is  to  go  through  the  heart  all  the 
time. 

101.  The  Heart  Beat. — The  heart  beats  on  an  average 
about  seventy-two  times  per  minute.  The  rate,  how- 
ever, varies  widely  with  rest  and  exercise,  health  and 
disease.  Besides,  some  persons  have  naturally  a 
higher  average  and  others  a  lower. 

TABLE  SHOWING  VARIATIONS  WITH  AGE 

At  birth,  from 140  to  130 

First  year,  from 130  to  115 

Second  year,  from 115  to  100 

Third  year,  from      .     .    \     .     .     .     .     .  100  to    90 

Seventh  year,  from  ........  90  to    85 

Fourteenth  year,  from  .     .     .•    .     .     .     .  85  to    80 

Adult,  from 80  to    70 

Old  age,  from 70  to    60 

Decrepit,  from 75  to    65 

Count  your  own  heart  beat  per  minute  at  different  times  of  the 
day,  for  different  positions  of  the  body,  and  under  different  condi- 
tions of  exercise  and  rest.  Each  person  should  know  his  own  pulse. 

When  does  the  heart  rest  ?  The  two  auricles  con- 
tract at  the  same  time  and  force  the  blood  into  the 
ventricles.  Then  they  relax  and  rest  while  the  two 
ventricles  work  together  and  force  the  blood  into  the 
arteries.  In  this  way  the  auricles  and  the  ventricles 
rest  a  little  more  than  half  the  time.  It  is  an  interest- 
ing fact  that  the  muscles  of  the  heart  contract  in  about 
the  same  time,  whether  it  beats  slow  or  fast.  Now  the 
faster  the  beat,  the  shorter  must  be  the  period  of  rest 
between  the  beats. 


136  HUMAN   PHYSIOLOGY  CHAP. 

102.  Sounds   of   the  Heart.  —  No  machine  can  work 
without  noise.     If  you  place  your  ear  over  the  region 
of    the    heart,    two   distinct   sounds    can   be    detected. 
They  occur  in   quick   succession,  followed  by  a    short 
pause.     The  first  of  these  is  a  long,  dull  sound,  caused, 
we  think,  by  the  sudden  sharp  contraction  of  the  ven- 
tricles.    The  second  is  a  sharp,  short  click  caused  by 
the  closing  of  the  semilunar  valves.     These  two  sounds 
are  said  to  resemble  the  syllables  "  loob,"  "dup." 

To  the  physician  these  sounds  indicate  the  condition 
of  the  heart.  He  has  an  instrument,  called  the  steth- 
oscope, by  means  of  which  he  can  study  the  heart 
sounds  very  accurately.  Any  change  in  their  normal 
pitch,  force,  or  rhythm  means  a  certain  organic  disturb- 
ance or  disease. 

103.  The    Pulse. — When     the    ventricles     contract 
blood   is   forced   out  into  the  arteries,  and  their  walls 
dilate  to  make  room  for  it.     At  every  beat  of  the  heart 

the  arterial  walls  bulge  out, 
for  they  are  as  elastic  as  rub- 
ber tubing.  Then  the  walls 
contract  and  push  the  blood 
onward,  causing  a  similar 
wave  elsewhere.  These  pul- 
sations in  the  arteries,  due  to 
FIG.  73. —  Showing  how  to  find  the  contraction  of  their  elastic 

the  pulse  (Scheinert).  ,.,  . 

walls,  constitute  ULQ  pulse. 

As  a  rule,  the  larger  arteries  lie  near  the  bones  and 
quite  removed  from  the  surface  of  the  body,  but  at  cer- 
tain places  they  come  near  the  surface.  Pulsations 


x  CIRCULATION  OF  THE   BLOOD  137 

of  the  radial  artery  at  the  wrist,  the  temporal  artery 
just  in  front  of  the  ear,  and  the  carotid  on  either  side 
of  the  larynx  can  be  easily  felt. 

104.  Alcohol  and  Tobacco.  —  Alcohol  acts  upon  the 
blood,  the  arteries,  and  the  heart  itself.  It  impov- 
erishes the  blood  by  acting  upon  the  corpuscles,  thus 
decreasing  its  capacity  for  carrying  oxygen.  The 
effect  upon  the  blood  vessels  is  to  dilate  them.  For 
this  reason  the  skin  looks  flushed  and  red ;  the  capil- 
laries become  enlarged ;  and  the  person  feels  warm 
while  the  body  is  really  giving  off  a  large  amount  of 
heat,  which  must  lower  the  temperature  of  the  body. 
It  is  said  that  deposits  of  fat  are  made  in  the  walls  of 
the  arteries  and  of  the  heart,  thus  weakening  and  pre- 
disposing them  to  disease. 

The  nerves  controlling  the  heart  and  arteries  are 
paralyzed  by  alcohol.  The  heart  now  acts  like  a  run- 
away horse,  beating  very  rapidly  and  attempting  to  fill 
the  much  distended  blood  vessels. 

The  nicotine  of  tobacco  acts  as  a  poison  on  the 
nerves  of  the  heart.  This  is  probably  its  most  harmful 
effect  upon  the  body.  The  heart  beat  becomes  irregu- 
lar and  less  vigorous.  The  nerves  are  no  longer  as 
delicate  and  sensitive  as  they  should  be.  The  smoker's 
heart  goes  on  beating  at  nearly  the  same  rate  day  and 
night,  thus  robbing  the  heart  of  a  certain  amount  of 
rest  that  is  necessary  to  keep  it  in  a  perfectly  healthy 
condition.  It  is  believed  by  scientists  that  many  of  the 
cases  of  fatal  heart  disease  may  be  traced  to  the  use  of 
tobacco. 


[38  HUMAN   PHYSIOLOGY  CHAP. 


SUMMARY'  OF  THE   MAIN   POINTS 

1.  The  heart  is  the  central  organ  of  circulation.     It  is  a 
hollow,  muscular  organ  situated  in  the  chest,  between  the  lungs, 
and  covered  with  the  pericardium. 

2.  The  heart  is  five  inches  long,  three  and  one  half  inches 
wide,  weighs  about  ten  ounces,  and  consists  of  four  chambers, 
—  two  auricles  and  two  ventricles. 

3.  The  tricuspid  valve  is  on  the  right  side  between  the  auri- 
cle and  ventricle,  and  the  mitral  on  the  left ;  and  the  semi- 
lunar  valves  are  at  the  beginning  of  the  arteries. 

4.  All  blood  vessels  leading  from  the  heart  are  called  arteries. 
They  have  heavy,  elastic,  muscular  walls,  and  carry  blood  to  all 
organs  and  tissues  of  the  body. 

5.  The  arteries  grow  smaller  and  smaller  until  they  shade 
off  into  the  very  thin  walled  capillaries.    These  are  so  numerous 
everywhere  that  you  cannot  pierce  the  skin  with  a  fine  needle 
without  injuring  several  of  them. 

6.  The  capillaries  unite  and  form  larger  vessels,  called  veins, 
which   grow  larger  and  larger  until  there  are  only  two  great 
trunks.     The  veins  return  the  blood  from  the  capillaries  to  the 
right  auricle. 

7.  Lymphatic  capillaries  begin  in  lymph  spaces  all  over  the 
body  and  serve  as  drainage  tubes  to  return  most  of  the  wastes 
into  the  blood. 

8.  The   thoracic   duct  returns   the  lymph  from    the    entire 
body  below  the  diaphragm  and  from  the  left  half  above   the 
diaphragm.     The   right   lymphatic  trunk  is  much  smaller ;    it 
returns  the  lymph  from  the  right  half  of  the  body  above  the 
diaphragm. 

9.  A  moderate  amount  of  daily  exercise  is  essential  to  the 
proper  circulation  of  both  blood  and  lymph.     The  wastes  stag- 
nating in  the  lymph  spaces  lead  to  disease. 


x  CIRCULATION  OF  THE   BLOOD  139 

10.  The  blood  flows  from  the  right  ventricle  to  the  lungs, 
where  it  is  oxygenated  ;  then  it  returns  to  the  left  heart,  from 
which  it  is  forced  out  into  the  aorta  that  distributes  it  by  means 
of  its  numerous  branches  to  all  the  capillaries  of  the   body. 
From  the  capillaries  it  enters  the  veins  and  is  brought  back  to 
the  starting  point. 

11.  The    blood    completes  one  entire  circulation  in  about 
twenty-two  seconds.     The  rate  of  flow  is  fastest  in  the  aorta 
and  arteries,  slower  in  the  veins,  and  slowest  in  the  capillaries. 

12.  The  chief  function  of  the  heart  is  to  pump  blood  into 
the  aorta  under  an  immense  pressure  that  causes  the  walls  of 
the  aorta   to  bulge  out  greatly.     These  elastic  walls  contract 
and  force  the  blood  onward  in  its  course. 

13.  The  heart  beats  about  seventy- two  times  per  minute  in 
the  adult.     The  two  auricles  work  together  and  then  the  two 
ventricles.     In  this  way  the  heart  rests  a  little  more  than  half 
the  time  when  beating  at  the  normal  rate. 

14.  The  first  sound  of  the  heart  is  long  and  dull,  and  occurs 
when  the  ventricles  contract.     The  second  is  short  and  sharp ; 
it  occurs  when  the  semilunar  valves  close. 

15.  The  walls  of  the  arteries  are  elastic,  like  rubber  tubes, 
and  distend  when  blood  is  forced  into  them  by  the  ventricles. 

1 6.  Alcohol  acts  on  the  red   corpuscles,  causing  them  to 
shrink.     It  acts  upon  the  walls  of  the  arteries  and  the  heart, 
causing  fatty  degeneration,  and  in  this  way  weakening  them. 
Alcohol   and    tobacco   both  have   a  -specific  action  upon  the 
nerves  that  control  the  size  of  the  blood  vessels  and  the  action 
of  the  heart. 


CHAPTER   XI 

FOODS   IN   THE   TISSUES 

105.  Review.  — We  have  traced  the  foods  and  oxygen 
into  the  blood   and  have   studied  the  organs  by  which 
the  blood  is  distributed  to  all  parts  of  the  body.     As  yet 
the  foods  have  been  of  no  value,  in  fact  they  have  been 
an  expense  at  every  step  without  yielding  any  return. 
Energy  has  been  used  in  cooking  and  preparing  foods 
for   the    table,    and    then    mastication,    digestion,    and 
absorption  have  cost  much  labor.     Then,  by  the  hard 
work  of  the  heart,  they  are  forced  through  the  arteries, 
capillaries,    and   veins.       But   while    the    blood    passes 
through  the  thin-walled  capillaries  much  of  the  oxygen, 
albumin,  sugar,  fats,  water,  and  salt  exudes  through  the 
walls  of  the  capillaries  and  forms  part  of  the  lymph. 
Now  the  foods  are  within  reach  of  the  cells ;  they  are 
soon  to  serve  their  real  purpose. 

106.  The  Lymph.  —  We  have  learned  something  about 
the  lymph  in  former  chapters.     It  is  quite  like  blood  in 
composition  except  that  it  contains  no  red    corpuscles 
because   they   cannot   pass   through    the   walls  of   the 
capillaries.     It  is  about  ninety  per  cent  water,  and  the 
remainder  consists  of  solids  held  in  solution.     The  cells 
select  from  the  blood  what  they  need  for  their  own  use, 

140 


CHAP,  XI 


FOODS   IN  THE  TISSUES 


141 


and  so  we  find  in  the  lymph  all  of  the  foods  that  occur 
in  the  blood.  Albumins,  sugars,  fats,  water,  salt,  and 
oxygen  are  all  present  in  the  right  proportions. 

The  cells  give  off  their  worn-out  and  waste  materials 
to  the  lymph.  These  are  carbon  dioxid,  water,  am- 
monia compounds,  and  many  other  products  in  small 
quantities.  Some  of  these  wastes  may  be  of  value  else- 
where in  the  body.  The  cells  live  in  this  liquid  medium, 


Musc/e  ce//s 


Lymjob 


FIG.  74.  —  Showing  the  relation  of  blood  capillaries  to  muscle  cells  anfl  to 
lymph  capillaries  (Zuppke). 

in  which  they  find  all  the  foods  they  need  and  to  which 
they  can  give  all  their  useless  and  worn-out  matter. 
The  lymph  serves  a  very  important  purpose  in  the  body. 
107.  The  Cell.  —  The  foods  found  in  the  lymph  are 
taken  into  the  cells  and  used  for  various  purposes.  The 
albumins  are  used  to  repair  the  cells  as  fast  as  they  are 
worn  out.  The  cells  would  wear  out  and  die  if  we  did 
not  eat  enough  proteid  food  stuffs  to  keep  them  repaired. 
The  albumins  may  also  be  oxidized  and  liberate  heat 
All  growth  is  due  to  the  albumins. 


142  HUMAN  PHYSIOLOGY  CHAP. 

The  sugars  and  fats  enter  the  cells  and  are  made  to 
combine  with  oxygen,  i.e.  to  burn  like  coal  in  a  furnace, 
and  produce  heat  to  keep  us  warm.  When  coal  is  burned 
it  produces  a  certain  amount  of  ash,  and  so  these  foods 
leave  wastes  that  must  be  removed  from  the  cells.  In 
some  strange  way  part  of  the  heat  derived  from  the 
oxidation  of  the  foods  is  changed  to  other  forms  of 
energy  and  enables  us  to  play,  to  work,  and  to  think. 

We  now  understand  why  oxygen  is  so  necessary  to 
life.  Coal  will  not  burn  when  the  drafts  of  the  stove 
are  closed  so  as  to  shut  off  all  the  air.  The  foods  could 
not  be  burned  in  the  cells  if  there  were  not  a  sufficient 
quantity  of  oxygen  present.  The  oxygen  is  made  to 
unite  with  sugars,  and  as  a  result  we  get  heat,  water, 
and  carbon  dioxid.  In  a  similar  way  it  will  unite  with 
the  carbon  of  the  fats  and  yield  heat,  water,  and  carbon 
dioxid.  The  process  of  growth  and  cell  repair  requires 
an  adequate  supply  of  this  important  gas.  When  we 
do  not  breathe  a  sufficient  amount  of  good,  pure  air,  the 
foods  cannot  be  properly  oxidized.  Instead  of  the  wastes 
that  should  be  formed  there  are  produced  partially  oxi- 
dized products  of  a  very  harmful  nature. 

Water  is  indispensable  not  only  in  the  blood  and 
lymph,  where  it  serves  as  a  solvent,  but  also  in  the  cell 
itself.  The  protoplasm  of  the  cell  has  a  large  percent- 
age of  water.  The  normal  activity  of  the  cell  cannot 
be  carried  on  without  a  liberal  supply  of  water.  Hence 
it  is  a  good  thing  to  drink  pure,  fresh  water  freely.  Salt 
is  not  oxidized,  but  it  seems  to  be  important  in  stimulat- 
ing and  regulating  the  activity  of  the  cells. 


xi  FOODS  IN  THE  TISSUES  143 

108.  The  Wastes.  —  The    oxidation  of    foods   in   the 
cells  gives  rise  to  certain  waste   products  that  must  be 
removed.     The  albumins  form  ivater  and  carbon  dioxid, 
and  ammonia  compounds,  as  kreatin.     From  the  sugars 
and  fats,  carbon  dioxid   and   water  are   the    important 
wastes.     Salt  and  water  leave  the  cells  in  the  form  in 
which  they  reached  them. 

These  wastes  are  produced  in  the  cell  and  then  given 
off  to  the  lymph.  What  becomes  of  them  ?  Most  of 
the  carbon  dioxid  enters  the  capillaries  of  the  blood 
and  is  carried  back  to  the  heart  by  means  of  the  veins. 
Then  it  goes  to  the  lungs,  where  it  is  given  off  to  the 
air  sacs  and  exhaled.  The  other  wastes  reach  the  blood 
through  the  lymphatics.  In  the  lymph  spaces  all  over 
the  body  there  begin  small  lymphatic  capillaries.  Much 
of  the  water,  salts,  kreatin,  etc.,  enters  the  open  mouths 
of  these  tiny  vessels  and  is  drained  away  by  them. 
These  wastes  reach  the  blood  through  the  great  lymph 
trunks  that  empty  into  the  subclavian  veins.  Now  the 
wastes  are  in  the  blood. 

109.  Changes  in  the  Blood.  —  Some  of  these  products 
may  be  of  value  to  other  cells  and  so  are  kept  in  the 
blood.     There    are   many   organs  of   the   body    whose 
chief  business  it  is  to  change  the  blood  as  it  circulates 
through  them.     The  liver  is  an  organ  of  this  kind.     We 
have  learned  some  things   about   the    liver  in   former 
chapters.     Besides  doing  the  things  mentioned  before, 
this  large  and  important  organ  serves  as  a  crematory  for 
certain  waste  products  that  come  from  the  cells.     Here 
urea  is  manufactured  from  ammonia  compounds.     The 


144  HUMAN   PHYSIOLOGY  CHAP. 

urea  then  enters  the  blood  and  is  carried  along  in  it 
until  the  kidney  is  reached,  where  it  is  picked  out  and 
removed  from  the  body. 

Among  the  other  organs  that  are  especially  helpful  in 
changing  the  blood  as  it  passes  through  them  may  be 
mentioned  the  pancreas,  the  thyroid  bodies,  the  adre- 
nals, the  lymph  nodes  and  perhaps  the  spleen.  The 
adrenals  are  small  bodies  just  above  the  kidneys,  and  it 
is  thought  that  they  produce  a  substance  that  has  an 
important  action  upon  the  heart  and  arteries. 

The  thyroid  bodies  are  situated  in  the  neck,  one  on 
either  side  of  the  trachea  near  its  upper  end.  They  are 
dark  red  in  color  and  somewhat  granular  in  structure. 
Sometimes  these  bodies  enlarge  very  much,  causing  the 
disease  known  as  goitre.  These  bodies  are  important  in 
two  ways  :  first,  they  remove  from  the  blood  certain 
poisons  made  by  the  action  of  the  cells ;  second,  they 
produce  a  substance  which  is  of  use  in  keeping  all  the 
organs  of  the  body  in  a  good  condition.  When  the 
thyroid  bodies  do  not  work  as  they  should  the  blood  is 
deprived  of  their  product,  and  the  person  suffers  from  a 
disease  known  as  thyroid  starvation. 

In  children  such  a  condition  may  result  in  a  form  of 
idiocy  (cretonism).  A  person  suffering  from  thyroid 
starvation  may  be  helped  by  eating  prepared  thyroid 
glands  obtained  from  the  sheep  or  the  calf.  The  large 
packing  houses  have  put  on  the  market  prepared  thyroid 
glands  for  this  purpose. 

The  spleen  is  located  in  the  abdomen  to  the  left  of  the 
stomach.  It  is  an  oblong,  flat,  reddish  gray  body  that 


xi  FOODS   IN  THE  TISSUES  145 

has  an  abundant  blood  supply.  The  spleen  is  small  dur- 
ing digestion,  but  grows  larger  a  few  hours  after  meals, 
reaching  its  greatest  size  about  the  fifth  hour,  and  then  it 
slowly  diminishes  to  its  usual  size.  It  is  always  small  in 
starved  animals.  This  organ  has  been 
carefully  studied  by  scientists,  but  they 
cannot  say  as  yet  what  functions  it 
performs.  It  is  thought  by  some  that 
it  aids  the  liver  in  changing  certain 
ammonia  compounds,  that  it  manufac- 
tures white  corpuscles,  and  that  it  helps  FlGt  75._ The  spleen, 
to  destroy  the  worn-out  red  corpuscles.  front  view  (ZuPPke)- 
The  spleen  has  been  entirely  removed  in  cases  of  disease 
without  causing  any  serious  injury.  It  may  be  that  other 
organs  carry  on  its  functions  when  the  spleen  is  removed. 
110.  Animal  Heat.  —  The  oxidation  of  foods  in  the  cells 
gives  rise  not  only  to  these  harmful  waste  products  but 
also  to  a  large  amount  of  heat.  We  know  the  fire  in  a 
furnace  or  stove  will  go  out  when  the  fuel  is  consumed. 
If  we  wish  to  have  it  burn  at  a  uniform  rate  fuel  must 
be  added  from  time  to  time.  The  temperature  of  the 
human  body  is  kept  at  about  98^°  F.  in  health.  Even  a 
very  slight  variation  from  the  normal  temperature  is 
accompanied  by  either  a  fever  or  a  chill.  In  man  a 
temperature  of  102°  F.  means  that  combustion  is  too 
rapid,  and  something  should  be  done  to  restore  it  to  the 
normal.  During  periods  of  starvation  or  great  prostra- 
tion, and  in  certain  diseases,  the  temperature  may  fall 
several  degrees  below  the  normal.  A  temperature  of 
92°  F.  usually  proves  fatal. 


i46  HUMAN   PHYSIOLOGY  CHAP. 

One  of  the  most  important  purposes  of  the  foods  we 
eat  is  to  furnish  heat  to  keep  us  warm  so  that  all  the 
cells  may  do  their  work  as  they  should.  The  oxidation 
of  fats  liberates  much  more  heat  than  can  be  obtained 
from  any  other  food  stuff.  That  is  the  reason  why  so 
much  fat  and  oil  is  eaten  by  people  living  in  cold  coun- 
tries. It  is  really  the  best  food  stuff  to  keep  them  warm. 
In  warm  climates,  however,  very  little  fat  is  eaten.  The 
proteids  and  carbohydrates,  when  completely  oxidized, 
are  about  equally  valuable  as  heat  producers ;  they  lib- 
erate about  half  as  much  heat  as  the  same  weight  of 
fat  does. 

About  ninety  per  cent  of  the  heat  produced  daily 
comes  directly  from  the  oxidation  of  the  foods  eaten. 
A  small  amount  comes  from  the  warm  substances  taken 
into  the  body,  and  from  the  friction  caused  by  the 
movement  of  the  blood,  the  action  of  the  muscles,  and 
from  still  other  sources. 

111.  Loss  of  Heat.  —  The  amount  of  heat  produced 
every  twenty-four  hours  is  very  great,  and  yet  the 
temperature  of  the  body  remains  unchanged.  What 
becomes  of  it  ?  About  one  fourth  of  the  heat  may  be 
transformed  into  mechanical  energy  and  used  in  doing 
work.  The  remaining  three  fourths  is  slowly  lost ;  it 
keeps  up  the  temperature  of  the  body,  and  then  some  of 
it  radiates  from  the  skin  into  the  surrounding  air,  which 
is  usually  cooler  than  the  body.  The  air  we  inhale,  the 
water  we  drink,  and  many  of  the  foods  we  eat  are  cooler 
than  the  body,  and  hence  some  of  the  heat  is  used  in 
raising  the  temperature  of  these  things.  All  of  the  wastes 


xi  FOODS  IN  THE  TISSUES  147 

that  leave  the  body,  as  the  exhaled  air,  the  sweat,  and 
the  material  excreted  from  the  kidneys  and  bowels, 
carry  with  them  a  large  amount  of  heat. 

112.  Regulation  of  Temperature.  — Some  animals  take 
on  the  temperature  of  the  medium  in  which  they  live. 
If  you  place  a  frog,  a  lizard,  or  a  fish  in  cold  water  for 
some  time,  its  blood  will  be  nearly  as  cold  as  the  water. 
Should  you  raise  the  temperature  of  the  water  slowly, 
they  would  adapt  themselves  to  great  changes.  The 
temperature  of  their  blood  depends  upon  and  is  regu- 
lated by  their  environment.  Such  animals  are  said  to 
be  cold  blooded. 

In  man  and  the  higher  animals  the  production  and 
loss  of  heat  are  controlled  by  the  nervous  system.  The 
skin  is  the  important  regulator  of  the  loss  of  heat. 
When  the  pores  of  the  skin  are  open  and  the  sweat 
glands  are  busily  at  work,  a  large  amount  of  heat  may 
be  lost  by  perspiration.  Again,  the  capillaries  of  the 
skin  may  dilate  and  expose  a  large  amount  of  blood  to 
the  surface  of  the  body,  from  which  heat  will  radiate 
rapidly.  All  this  is  controlled  by  the  nerves  of  the 
skin. 

The  kind  and  amount  of  clothing  we  wear  are  impor- 
tant factors  in  regulating  the  loss  of  heat  from  the  skin. 

SUMMARY   OF  THE   MAIN   POINTS 

1.  Lymph  is  blood  without  red  corpuscles.     It  contains  all 
the  foods  and  wastes  of  the  cells. 

2.  Albumins   are    the    building    and    repairing   foods.     No 
growth  occurs  without  them.     They  are  also  oxidized. 


148  HUMAN   PHYSIOLOGY  CHAP,  xi 

3.  The  fats  and    sugars   are    oxidized   and    produce    heat. 
Their  wastes  are  carbon  dioxid  and  water. 

4.  Water  and  salt  are  not  changed  in  the  cells  but  are  im- 
portant in  building  up  and    repairing   and  in  stimulating  the 
cells  to  activity. 

5.  Carbon    dioxid,    ammonia    compounds,    and    all    other 
waste  materials  formed  in  the  cells  are  given  off  to  the  lymph. 

6.  The    carbon  dioxid  enters  the  blood  capillaries  and  is 
carried  to  the  lungs,  where  it  is  selected  out  of  the  blood  and 
exhaled  from  the  body. 

7.  The  other  wastes  are  drained  off  through  the  lymphatics 
which  finally  empty  into  the  subclavian  veins  near  the  base  of 
the  neck. 

8.  The    liver,   pancreas,    thyroid    bodies,    adrenals,    lymph 
nodes,  and  perhaps  the  spleen  are  active  in  producing  impor- 
tant changes  in  the  blood  as  it  circulates  through  them. 

9.  The  useless  proteid  products  are  changed  to  urea  in  the 
liver  and  thrown  back  into  the  circulation. 

10.  The  oxidation  of  foods  in  all  cells  of  the  body  produces 
a  large  amount  of  heat  that  is  used  to  maintain  the  body  tem- 
perature at  981°  F.  and  to  furnish  energy.     Friction  produces 
a  small  amount  of  heat. 

11.  The  heat  is  lost  by  (i)  radiation  from  the  skin,  (2)  the 
escape  of  watery  vapor  from  the  lungs  and  skin,  and  (3)   the 
excretion  of  material  from  the  kidneys  and  bowels. 

12.  There  are  nerves  which  regulate  the  production  and  the 
loss  of  heat. 


CHAPTER   XII 

THE   SKIN   AND    THE   KIDNEYS 

113.  Review.  —  We  have  traced  the  foods  from  the 
time  they  entered  the  mouth  through  the  many  changes 
of  digestion,  absorption,  circulation,  and  oxidation  in 
the  cells,  until  they  were  finally  changed  into  useless 
substances.  They  have  served  their  purpose.  The  re- 
moval of  the  wastes  from  the  body  is  just  as  important 
to  health  as  the  taking  of  nutritious  foods.  A  large 
city  has  trains  and  boats  bringing  food  to  supply  its 
inhabitants,  but  equally  important  and  often  more  diffi- 
cult to  solve  is  the  problem  of  how  to  get  rid  of  the 
garbage  and  sewage. 

In  the  body  we  find  certain  organs  whose  chief  busi- 
ness it  is  to  remove  the  wastes  from  the  blood  and  to 
eliminate  them  from  the  body.  The  lungs,  intestines, 
skin,  and  kidneys  together  keep  these  useless  and  harm- 
ful products  from  accumulating  in  the  blood.  They  are 
the  organs  of  excretion.  We  have  learned  that  the 
lungs  remove  carbon  dioxid,  and  the  large  intestine 
removes  certain  indigestible  parts  of  the  foods  and 
wastes  poured  into  the  alimentary  canal.  We  shall  now 
study  the  skin  and  the  kidneys  to  see  what  part  they 
play  in  removing  the  wastes  from  the  body. 

149 


'50 


HUMAN   PHYSIOLOGY 


CHAP. 


114.  The  Skin.  —  The  skin  is  a  soft,  tough,  loosely 
fitting  covering  of  the  entire  surface  of  the  body.  It  is 
really  somewhat  like  the  mucous  lining  of  the  respira- 
tory and  digestive  organs.  Under  the  skin  we  find  a 
layer  of  fatty  substance  which  serves  as  a  kind  of 
blanket  to  keep  us  warm  in  cold  weather,  protect  the 
delicate  parts  beneath  against  injury,  and  to  round  out 
the  form,  making  it  more  beautiful.  In  old  age,  long 
sickness,  and  starvation  this  fat  may  be  used  by  the 
cells,  and  the  person  grows  thin  and  the  skin  becomes 
wrinkled. 

The  skin  consists  of  a  thin  outer  layer,  the  epidermis, 
cuticle,  or  scarf  skin,  and  of  a  thicker  under  layer,  the 

dermis,  cutis,  or  true 


Epidermis 


Hair  . 

skin.       1  he    raised 

part  of  a  blister  is 
the  epidermis. 
When  this  is  cut 
away  the  dermis 
may  be  seen  below. 
The  epidermis 
consists  of  round 
and  flat  epithelial 
cells  closely  packed 
together  so  as  to  form  a  very  firm  but  thin  protecting 
membrane  for  the  dermis.  On  the  soles  of  the  feet 
and  the  palms  of  the  hands  the  epidermis  is  quite  thick. 
A  callus  may  develop  in  the  epidermis  whenever  it  is 
subjected  to  pressure  for  a  long  time.  There  are  neither 
nerves  nor  blood  vessels  in  the  outer  layer,  The  rounded 


FlG.  76.  —  A  vertical  section  of  the  skin 
(Newell). 


xii  THE  SKIN   AND  THE   KIDNEYS  151 

epithelial  cells  in  the  under  surface  are  nourished  by 
lymph  that  comes  from  the  capillaries  of  the  dermis, 
while  the  flattened,  dead,  horny,  or  scaly  cells  of  the 
outer  surface  need  no  nourishment.  These  cells  are 
continually  dropping  off.  In  the  deeper  parts  of  the  epi- 
dermis we  find  very  tiny  particles  of  coloring  matter 
known  as  the  pigment.  In  different  persons  and  races 
the  pigment  varies  in  color  from  a  pale  pink  to  a  dark 
brown  or  black ;  and  in  amount,  from  none  at  all  in 
albinos  and  a  little  in  white  persons,  to  a  great  abun- 
dance in  deep-black  negroes.  Sometimes  the  pigment 
is  not  evenly  distributed,  but  occurs  in  patches  called 
freckles.  The  complexion  depends  upon  the  kind  and 
amount  of  pigment  in  the  scarfskin. 

The  dermis  is  well  supplied  with  blood  vessels  and 
nerves.  The  epidermis  dips  down  into  the  true  skin 
between  little  projections  called  papillce.  In  these  pa- 
pillae of  the  dermis  are  located  the  nerve  endings  which 
enable  us  to  have  sensations  of  touch,  pain,  and  tem- 
perature. 

115.  Glands  of  the  Skin.  —  In  the  skin  are  found  two 
kinds  of  glands  secreting  very  different  fluids.  They 
are  the  oil  or  sebaceous  glands,  and  the  siveat  glands. 

The  sweat  glands  are  long,  convoluted  tubes  extend- 
ing down  into  the  true  skin  and  opening  by  small  pores 
on  the  surface  of  the  epidermis.  These  glands  occur  in 
the  skin  everywhere  but  are  most  numerous  in  the  palms  of 
the  hands  and  the  soles  of  the  feet.  It  has  been  estimated 
that  in  man  there  are  between  two  and  three  millions  of 
sweat  glands.  These  glands  are  constantly  active,  se- 


'52 


HUMAN   PHYSIOLOGY 


CHAP. 


creting  sweat.  Usually  the  secretion  evaporates  as  soon 
as  it  reaches  the  surface  of  the  skin,  and  you  would  not 
know  that  the  glands  were  at  work  at  all.  This  we  call 
insensible  perspiration.  On  very  hot  days  or  during 
vigorous  exercise"  the  amount  may  be  so  great  as  to 
accumulate  in  drops  that  can  be  seen  on  the  surface  of 
the  skin.  This  we  call  sensible  perspiration.  About  two 

pounds  or  one  quart 
of  perspiration  is  pro- 
duced on  an  average 
every  tiventy -four 
hours,  and  a  very  much 
greater  amount  on  a 
very  hot  day.  The 
purpose  of  tJie  sweat 
glands  is  to  remove 
from  the  blood  or- 
ganic wastes,  salts, 
and  water;  and  hence 
we  call  them  true 
organs  of  excretion. 
They  have  still  an- 
other function  more  important  than  this.  A  large 
amount  of  heat,  about  eighty  per  cent  of  all  that  leaves 
the  body,  escapes  through  the  skin.  It  is  the  perspira- 
tion evaporating  from  the  surface  of  the  skin  that  cools 
the  body  when  there  is  danger  of  becoming  overheated. 
In  this  way  the  skin  regulates  the  body  temperature. 

The   oil    or   sebaceous  glands  are  situated  near   the 
roots  of  the  hairs  and  pour  their  secretions  into  the  little 


FIG.  77. —  A  piece  of  skin  of  the  palm  of 
the  hand,  showing  pores  of  the  sweat 
glands,  and  grooves  between  the  papillae 
(Newell). 


xii  THE   SKIN  AND   THE   KIDNEYS  153 

pits,  called  hair  follicles,  in  which  the  roots  of  the  hairs 
are  embedded.  They  secrete  a  natural  oil  for  the  hair 
and  skin.  This  keeps  the  skin  in  a  soft  and  pliable 
condition  and  protects  the  body  against  absorbing  too 
much  moisture  from  the  air.  These  glands  are  espe- 
cially numerous  on  the  face  but  occur  all  over  the  body 
except  on  the  soles  and  palms. 

116.  Appendages  of  the  Skin.  —  On  the  end  of  each 
finger  and  toe  the  true  skin  is  covered  by  a  piece  of 
very  much  modified  horny  epidermis  called  a  nail.  The 
sides  and  root  of  the  nail  are  covered  by  folds  of  the 
skin  in  such  a  way  as  to 
make  a  little  pocket,  out 
of  which  the  nail  appears 
to  grow.  The  nails,  like 
the  epidermis,  are  without 
nerves  and  blood  vessels. 

The  nail  itself  is  COlorleSS       FIG.  78.  — A  vertical  section  of  a  finger 

and     quite      transparent.  naii  (Zuppke). 

The  pink  color  is  due  to  numerous  capillaries  in  the  nail 
bed  beneath.  Nails  grow  by  the  formation  of  new  cells  at 
their  roots,  which  slowly  push  the  nail  forward.  If  the 
epidermis  overhanging  the  root  and  the  sides  of  the 
nail  is  not  carefully  pushed  back  every  few  days,  it  may 
become  broken  and  tear  up  into  the  flesh,  forming  the 
so-called  hangnails.  The  hangnails  should  not  be  pulled 
out  but  cut  off  close  to  the  skin.  Besides  being  very 
painful,  they  offer  little  openings  through  which  poison- 
ous matter  may  enter  the  blood.  The  nails  should  be 
washed  with  soap  and  warm  water  and  carefully  cleaned 


154 


HUMAN   PHYSIOLOGY 


CHAP. 


with  a  nail  brush.  A  knife  should  never  be  used,  except 
for  trimming  the  nails.  It  is  best  to  cut  the  ringer  nails 
in  a  curved  direction  and  the  toe  nails  straight  across. 

The  entire  body,  except  the  palms  and  soles,  is  cov- 
ered with  a  growth  of   hair,   fine  and  scanty  in   some 

places  and  coarse 
and  abundant  in 
others.  A  hair 
consists  of  two 
parts:  a  ska  ft 
above  the  surface 
of  the  skin,  and 
a  root  beneath, 
placed  in  a  little 
sac  or  pocket  of 
epidermis  called 
\.\\Q  follicle.  Some- 
times the  follicle 
extends  down 
through  the  true 


B/ootf vessel 
•Nerve 


FlG.  79.  —  Showing  a  hair  follicle.     (Modified  from 
Heitzmann  by  Zinns.) 


skin  into  the  layer 
of  fatty  tissue 
below.  Blood  ves- 
sels enter  the  fol- 
licle at  the  lower 

end,  carrying  nourishment  to  the  root,  where  the  hair 

grows  by  the   constant  formation  of    new  cells  which 

slowly  push  the  hair  upward. 

77?^  color  of  the  hair  is  due  to  small  air  bubbles  and 

pigment  cells  in  the  hair  substance.    In  old  age  no  color- 


xii  THE   SKIN   AND   THE   KIDNEYS  155 

ing  matter  is  deposited  in  the  hair,  and  it  becomes  gray. 
Nerves  and  little  fibers  of  muscles  are  in  contact  with 
the  hair  follicles.  It  is  by  means  of  these  muscles  that 
the  skin  ruffles  to  form  goose  pimples  and  the  hairs 


FlG.  80.  —  Showing,  in  A,  muscle  fibers  at  rest  and  hairs  in  usual  position,  and, 
in  B,  muscle  fibers  contracted  and  hairs  standing  on  end.  (Modified  from 
Hall  by  Zinns.) 

"  stand  on  end."  The  hair  has  various  useful  functions 
besides  serving  to  adorn  the  human  body.  The  growth 
on  the  head  protects  us  against  cold,  and  excessive  heat 
from  the  sun's  rays,  and  against  the  effect  of  blows. 
The  eyebrows,  eyelashes,  and  the  hair  of  the  nose  and 
ears  all  serve  as  protecting  organs. 

The  hair  should  be  washed  or  shampooed  often  enough 
to  keep  the  scalp  clean  and  free  from  dandruff.  For 
this  purpose  any  good  toilet  soap  may  be  used.  A  stiff 
hair  brush  and  a  coarse  comb  with  blunt  teeth  should  be 
freely  used  to  keep  the  scalp  in  good  condition  and  the 
hair  in  order.  If  the  scalp  is  pale  and  the  hair  thin,  a 
daily  massage  of  a  few  minutes  will  improve  the  circu- 
lation, and  tend  to  increase  the  growth  of  the  hair. 

117.  Care  of  the  Skin.  — We  have  seen  that  the  skin 
is  one  of  the  chief  organs  for  removing  wastes,  ranking 


156  HUMAN   PHYSIOLOGY  CHAP. 

next  to  the  kidneys  in  the  excretion  of  water  and  organic 
matter,  and  have  also  learned  that  it  is  the  chief  organ 
for  controlling  and  regulating  the  body  temperature. 
It  forms  an  admirable  protecting  membrane,  being  tough 
and  firm,  and  at  the  same  time  very  pliaole ;  this  is  its 
most  important  function.  The  skin  is  also  an  organ  of 
respiration,  for  not  only  are  water  and  organic  waste 
products  eliminated  through  the  capillaries  of  the  skin, 
but  quite  a  large  amount  of  oxygen  is  taken  in  through 
it.  In  certain  diseases  the  patient  is  immersed  in  a 
warm  nutrient  bath,  as  milk,  and  enough  food  may 
enter  the  blood  through  the  skin  to  nourish  the  body. 
We  may  then  call  it  an  organ  of  absorption.  It  is  also 
the  organ  of  touch  and  temperature.  Because  it  does  so 
many  things  it  should  be  given  special  care.  How  can 
we  care  for  the  skin  ?  There  are  really  only  two  impor- 
tant things  to  bear  in  mind.  One  is  regular  bathing 
and  the  other  proper  clothing.  Of  course  the  kind  and 
amount  of  food,  exercise,  and  rest,  as  well  as  the  gen- 
eral condition  of  the  body,  are  important  in  keeping  the 
skin  in  a  good,  healthy  condition. 

118.  Bathing.  —  The  value  of  bathing  as  a  sanitary 
measure  is  not  sufficiently  understood  and  appreciated 
at  present  by  most  people.  Let  us  see  what  some  of 
the  results  are.  In  the  first  place  bathing  serves  to 
cleanse  the  skin  from  dirt,  oils,  and  waste  matters  that 
continually  accumulate  on  it.  The  perspiration  pores 
may  be  closed  up  if  all  such  matter  is  not  washed  off. 
Keeping  the  pores  open  and  the  skin  clean  aids  very 
much  in  preventing  colds,  fevers,  skin  eruptions,  and 


xii  THE   SKIN   AND   THE   KIDNEYS  157 

contagious  diseases  of  all  kinds.  It  also  increases  the 
digestive  and  assimilative  powers  in  general. 

Baths  may  be  classed  as  hot,  warm,  tepid,  cool,  and 
cold  water  baths,  depending  upon  the  temperature  of  the 
water  used ;  and  as  Turkish,  Russian,  Roman,  mineral, 
sea,  and  mud  baths.  The  cold  bath  should  be  taken 
the  first  thing  in  the  morning  or  some  time  after  break- 
fast. Its  chief  value  is  in  contracting  the  pores  and  blood 
vessels  of  the  skin  and  driving  the  blood  to  the  internal 
organs ;  increasing  the  respiration ;  diminishing  the 
pulse ;  lowering  the  temperature ;  and  stimulating  the 
nervous  system.  Upon  coming  out  of  the  bath  a  reaction 
should  follow  at  once.  The  capillaries  dilate,  the  respira- 
tion and  heart  beat  become  normal,  the  temperature  rises 
somewhat,  causing  a  feeling  of  warmth  and  buoyancy. 
This  reaction  may  be  hastened  by  rubbing  the  skin 
vigorously  with  a  rough  towel.  Many  find  a  cold 
sponge  or  shower  bath  preferable  to  a  plunge,  especially 
during  cold  weather.  A  cold  bath  taken  every  morning 
renders  a  person  almost  immune  against  colds  which 
are  so  common  at  certain  seasons  of  the  year.  A 
person  not  accustomed  to  the  cold  bath  must  exercise 
great  care  in  becoming  habituated  to  it. 

The  warm  bath  has  a  very  different  effect  and  is 
taken  at  a  different  time  and  for  quite  another  purpose. 
It  opens  the  pores  and  dilates  the  capillaries  of  tjie 
skin ;  forces  the  blood  to  the  surface ;  increases  the 
perspiration ;  quickens  respiration  and  the  heart  beat ; 
raises  the  body  temperature ;  and  soothes  the  nervous 
system  often  to  such  an  extent  as  to  make  the  person 


158  HUMAN   PHYSIOLOGY  CHAP. 

drowsy  and  sleepy.  When  the  muscles  feel  sore,  as 
after  severe  physical  exertion,  a  warm  bath  will  afford 
almost  immediate  relief.  Those  who  find  it  difficult  to 
go  to  sleep  may  find  a  warm  bath  just  before  retiring 
very  helpful. 

The  tepid  and  cool  bath  have  no  special  physiologic 
virtue  and  are  taken  for  the  purpose  of  cleansing  the 
skin.  The  other  baths  are  generally  employed  for 
their  medical  effects,  when  recommended  by  a  physician, 
and  need  not  be  discussed  here. 

Many  suppose  the  sea  bath  to  possess  wonderful 
virtues.  The  novelty,  change  of  scene,  fresh,  pure 
ocean  air,  together  with  the  cheerfulness  with  which 
seashore  life  is  accompanied,  go  far  to  make  up  the 
advantages  said  to  come  from  sea-bathing. 

The  soap  used  in  bathing  serves  to  dissolve  the 
grease  and  oil,  and  so  is  necessary  to  a  thorough  cleans- 
ing. Any  good  toilet  soap  may  be  safely  employed  by 
most  persons.  The  so-called  medicated  soaps  possess 
little  virtue. 

The  best  time  to  take  a  bath  is  a  short  time  before  a 
meal  or  from  three  to  four  hours  after  it.  The  very 
strong  can  take  a  bath  any  time  of  day,  but  most  persons 
must  exercise  some  judgment  in  the  matter.  Those 
who  take  a  cold  bath  will  find  it  most  invigorating  in 
the  morning ;  it  should  never  be  taken  after  fatiguing 
exercise  or  just  before  retiring.  Both  the  kind  and 
time  of  bathing  are  subject  to  wide  individual  differ- 
ences and  should  be  adapted  to  the  age,  occupation,  and 
general  health  and  temperament  of  the  person.  No 


xii  THE   SKIN   AND   THE   KIDNEYS  159 

specific  directions  can  be  given  for  all  to  follow.  Just 
as  in  eating  and  in  many  other  matters,  each  person 
may  choose  for  himself  within  certain  general  limits 
that  apply  to  all. 

119.  Clothing.  —  The  chief  purposes  of  clothing  are  : 
(i)  to  help  the  skin  regulate  the  body  temperature  by 
keeping  in  the  animal  heat  in  cold  weather  and  by 
permitting  it  to  escape  in  warm  weather;  (2)  to  protect 
the  body  against  heat,  dust,  and  other  uncomfortable  and 
harmful  influences  of  our  environment ;  (3)  to  satisfy 
the  feeling  among  civilized  nations  that  the  body  as  a 
whole  should  be  covered  ;  and  (4)  to  adorn  and  beautify 
the  body  by  wearing  clean  and  well-fitting  garments. 
The  last  purpose  is  often  allowed  to  become  so  impor- 
tant as  to  interfere  seriously  with  the  physiologic  and 
hygienic  purposes  mentioned  first. 

All  clothing  should  fit  all  parts  of  the  body  loosely. 
Tight  clothing  should  be  avoided,  for  it  checks  the  cir- 
culation of  the  blood,  interferes  with  the  natural  functions 
of  the  organs  and  with  physical  comfort  in  general.  All 
parts  of  the  body  should  have  the  utmost  freedom.  The 
arms  and  legs  should  not  be  restricted  in  their  move- 
ment ;  the  chest  should  be  free  to  enlarge  in  all  direc- 
tions ;  and  the  stomach,  liver,  kidneys,  and  intestines 
should  not  be  pushed  out  of  position.  There  is,  perhaps, 
no  part  of  the  body  more  abused  from  poorly  fitting 
clothing  than  the  feet.  How  often  shoes  are  purchased 
to  "  fit  the  head  "  and  not  the  feet !  Swellings,  corns, 
bunions,  ingrowing  nails,  and  other  deformities  and 
diseases  of  the  feet  are  in  every  case  the  result  of  shoes 


i6o 


HUMAN   PHYSIOLOGY 


CHAP. 


that  do  not  fit  the  feet.  Shoes  may  be  too  large,  too 
small,  or  uncomfortable  for  some  other  reason.  The 
French  heel  and  the  long,  pointed  toe  do  not  fit  any 
foot.  Tight  bands,  as  elastic  garters  or  elastic  shoe 

tops,  interfere  with  the  circula- 
tion of  the  blood,  causing  the 
veins  to  enlarge  permanently. 
Tight  clothing  may  seriously 
impair  the  health.  In  this 
whole  matter  the  one  impor- 
tant caution  to  heed  may  be 
stated  in  this  way  :  All  cloth- 
ing should  permit  the  utmost 
freedom  of  movement  to  all 
organs  and  members  of  the 
body  and  contribute  to  the 
fullest  extent  to  our  physical  comfort. 

The  amount  of  clothing  should  be  ample  to  keep  the 
body  in  a  comfortable  condition,  but  not  tend  to  cause 
free  perspiration.  There  is  danger  in  wearing  more 
clothing  in  cold  weather  than  is  really  necessary,  be- 
cause any  part  of  the  body  constantly  overheated 
becomes  tender  and  highly  sensitive  to  the  slightest 
ordinary  changes  in  temperature.  MufHers,  tippets,  or 
fur  collars  worn  about  the  neck  are  the  cause  of  many  a 
sore  throat  and  cold.  The  parts  of  the  body  that  require 
most  clothing  are  the  stomach  and  chest,  the  back  and 
shoulders.  More  clothing  is  necessary  in  the  evening 
than  during  the  day,  for  the  system  liberates  less  heat  at 
night.  Damp  and  wet  garments  are  dangerous  because 


FIG.  81.  —  Showing,  in  A,  a  foot 
distorted  by  tight  shoes,  and, 
in  Bt  a  natural  foot  (Zuppke). 


XII 


THE   SKIN   AND  THE  KIDNEYS 


161 


they  take  heat  from  the  body  and  hence  lower  its  tem- 
perature very  fast.  All  garments  worn  at  night,  as 
well  as  the  bedclothes,  should  be  thoroughly  aired  and 
sunned  every  morning  so  as  to  keep  them  perfectly  dry 
and  free  from  disease  germs. 

120.  The  Kidneys.  —  The  kidneys  are  bean-shaped 
organs,  about  four  inches  long  and  two  inches  wide, 
located  in  the  back  part 
of  the  abdomen,  just  be- 
low the  last  rib,  one  on 
either  side  of  the  back- 
bone. They  are  covered 
with  a  capsule  of  fat.  In 
appearance  the  kidneys  in 
man  are  quite  like  those 
of  the  sheep.  There  are 
two  quite  distinct  layers 
in  the  kidneys,  the  cortex 
on  the  outside  and  the 
medulla  on  the  inside.  In 
structure,  the  kidney  re- 
sembles the  skin  in  many 
ways.  If  you  can  imag- 
ine a  small  piece  of  skin 
turned  inside  out,  with  the 
two  layers  thickened  considerably  and  folded  up  in  the 
shape  of  a  bean,  you  have  some  idea  of  the  real 
structure  of  the  kidney.  Like  the  skin  they  contain 
glands  in  the  cortex,  and  many  long,  fine  tubules  wind- 
ing back  and  forth  in  the  cortex  and  medulla.  These 


FlG.  82. — A  longitudinal  section  of  the 
kidneys  (Huxley)  :  Cf,  cortex;  m, me- 
dulla; Py,  pyramid  in  the  medulla; 
P.  pelvis;  U,  ureters;  RA,  renal 
artery. 


1 62 


HUMAN   PHYSIOLOGY 


CHAP. 


tubes  finally  empty  their  excretion  into  an  open  space 
near  the  concave  surface  of  the  kidney,  called  the  pelvis. 
The  glands,  tubules,  and  pelvis  are  lined  with  a  mucous 
membrane,  thick  in  some  parts  and  thin  in  others. 

The  kidneys  are  very  useful   because  they  are    the 
principal   organs  for  the  removal  of    water,  urea,  and 

other  waste  matters.  In  warm 
weather  the  skin  probably 
removes  as  much  water  as 
the  kidneys  do.  The  skin 
also  excretes  some  salt  and 
urea,  but  most  of  these  wastes 
are  removed  through  the  kid- 
neys. Urea  is  manufactured 
from  ammonia  compounds  in 
the  liver.  It  then  enters  the 
blood  and  is  distributed  to  all 
parts  of  the  body.  When  the 
renal  arteries  carry  it  to  the 
glands  and  tubules  of  the  kid- 
neys, it  is  picked  out  of  the 
blood  and  poured  into  the  pel- 
vis. The  solid  urea  and  other 
poisonous  wastes  are  dissolved  in  a  large  amount  of 
water ;  this  is  known  as  urine.  All  urine  is  carried  from 
the  pelvis  of  the  kidneys  to  the  bladder  by  means  of  the 
ureters,  slender  ducts  about  sixteen  inches  long.  The 
bladder  serves  as  a  reservoir  for  the  urine,  from  which 
it  is  periodically  discharged  from  the  body.  About  three 
pints  of  urine  are  discharged  from  the  body  every  day. 


FIG.  83.  —  The  kidneys  and  blad- 
der (Cheever). 


xii  THE   SKIN  AND   THE   KIDNEYS  163 

121.  Diseases  of  the  Kidneys.  —  The  chief  causes  of 
diseases  of  the  kidneys  are  the  following :  exposure 
to  cold,  failure  to  keep  the  skin  clean  and  its  pores  open, 
excessive  use  of  alcoholic  beverages,  indulgence  in  harm- 
ful condiments,  as  mustard,  pepper,  etc.,  displacement 
of  these  organs  due  to  unhygienic  postures  of  the  body 
and  tight  clothing,  infection  by  certain  bacteria,  and 
habitually  eating  too  much  rich  foods  that  are  imper- 
fectly oxidized  in  the  cells.  How  do  colds  affect  the 
kidneys  ?  There  is  a  close  relation  between  the  skin 
and  kidneys,  and  when  the  pores  of  the  skin  are  closed, 
and  the  blood  is  driven  to  the  internal  organs  because 
of  prolonged  cold,  the  kidneys  must  excrete  the  wastes 
ordinarily  removed  by  the  skin,  and  at  the  same  time 
care  for  the  extra  amount  of  blood  forced  to  them. 
This  extra  work  the  kidneys  will  do  as  long  as  they  can, 
but  sooner  or  later  they  become  diseased  from  inflam- 
mation and  overwork. 

All  diseases,  as  measles,  scarlet  fever,  etc.,  accom- 
panied by  an  eruption  or  rash  on  the  skin,  cause  a  con- 
gestion and  inflammation  of  the  kidneys  that  make  them 
weak  and  especially  liable  to  disease.  During  and 
immediately  following  such  diseases  t  it  is  necessary  to 
see  that  the  kidneys  are  not  exposed  to  cold  nor  over- 
worked. 

If  the  kidneys  be  removed  from  an  animal,  it  can  live 
only  a  few  hours.  The  poisonous  wastes  accumulate  in 
the  blood  and  soon  cause  blood  poisoning.  When  these 
organs  are  diseased,  the  functions  of  all  the  organs  of 
the  body  are  impaired.  The  proper  removal  of  the 


1 64  HUMAN   PHYSIOLOGY  CHAP. 

wastes  is  a  very  important  matter  that  cannot  be  neg- 
lected without  serious  danger. 

122.  The  Effect  of  Alcohol  upon  the  Skin  and  Kidneys. 
—  We  have  already  learned  that  alcohol  acts  upon  the 
blood  vessels,  causing  them  to  dilate  and  so  giving  the 
skin  a  characteristic  flushed  and  red  appearance.  The 
body  feels  warm,  but  as  a  matter  of  fact  heat  rapidly 
radiates  from  the  engorged  capillaries  of  the  skin,  caus- 
ing a  greater  loss  of  heat  and  a  consequent  lowering  of 
the  temperature.  The  nerves  controlling  the  surface 
circulation  and  regulating  the  body  temperature  are 
paralyzed  by  alcohol. 

The  effect  of  alcoholic  beverages  upon  the  kidneys  is 
very  marked.  The  delicate  capillaries  going  to  the 
glands  and  tubules  dilate,  causing  congestion  and  inflam- 
mation. Under  this  condition  the  kidneys  are  stimulated 
to  overaction.  Besides  this  the  structure  of  these  organs 
may  be  so  changed  that  they  cannot  properly  perform 
their  functions.  The  irritation  due  to  the  continued  use 
of  alcoholic  drinks  is  thought  to  be  one  of  the  chief 
causes  of  the  fatal  disease  of  the  kidneys  named 
"  Bright's  Disease,"  after  the  English  physician  who 
first  described  it  In  this  dreaded  disease  the  functions 
of  the  kidneys  are  so  deranged  that  albumin  is  excreted 
instead  of  urea  and  other  wastes.  The  good  albumin 
so  important  in  building  up  and  repairing  the  cells  is 
eliminated  from  the  body,  while  useless  and  harmful 
waste  matters  remain  in  the  blood.  In  the  disease 
known  as  diabetes  an  excessive  amount  of  sugar  appears 
in  the  excretion  from  the  kidneys. 


xii  THE   SKIN   AND  THE   KIDNEYS  165 


SUMMARY   OF  THE   MAIN   POINTS 

1.  The  skin  consists  of  an  outer  layer,  the  epidermis,  and 
below  this  a  thicker  layer,  the  dermis  or  true  skin. 

2.  The  most  important  function  of  the  skin  is  to  protect 
the  body  against  foreign  substances.     It  is  firm  and  tough,  but 
very  pliable. 

3.  A  thick  layer  of  fatty  tissue  is  deposited  under  the  der- 
mis.    This  serves  as  a  food  supply  in  case  of  sickness,  as  a 
blanket  to  keep  us  warm  in  cold  weather,  and  to  give  round- 
ness and  beauty  to  the  human  body. 

4.  The  epidermis  consists  of  epithelial  cells  held  together 
by  a  small  amount  of  cement.     No  blood  vessels,  nerves,  or 
lymphatics  occur  in  it. 

5.  In  the  deeper  parts  of  the  epidermis  are  found  the  pig- 
ment cells  that  give  color  to  the  skin. 

6.  The  dermis  is  well  supplied  with  blood  vessels,  lymphat- 
ics, and  nerves. 

7.  The  sweat  glands  of  the  skin  are  for  the  purpose  of  re- 
moving water,  salt,  and  small  amounts  of  other  wastes.     About 
a  quart  of  perspiration  is  excreted  on  a  temperate  day. 

8.  The  oil  glands  secrete  a  small  amount  of  oil  which  lubri- 
cates the  hair,  keeps  the  skin  soft  and  pliable,  and  protects  the 
body  against  moisture. 

9.  The  skin  is  the  most  important  organ  for  controlling  the 
body  temperature. 

10.  The  nails  and  hairs  are  two  important  structures  made 
of  highly   modified    epidermis.     They   serve    to    protect   and 
beautify  the  body  when  properly  cared  for. 

11.  The  functions  of  the  skin  are  to  serve  as  a  protecting 
covering ;  to  regulate  the  body  temperature  ;  to  remove  certain 
waste  products  ;  to  furnish  the  sense  of  touch  and  temperature  ; 
to  aid  in  respiration ;  and  to  act  as  an  absorbing  surface. 


1 66  HUMAN   PHYSIOLOGY  CHAP,  xn 

12.  The  skin  may  be  kept  clean  and  in  a  healthy  condition 
by  proper  bathing  whenever  necessary.     This  may  be  twice  a 
week  or  oftener,  depending  upon  the  season  and  occupation. 

13.  A  cold   sponge,  shower,  or  plunge  bath   taken  in  the 
morning  has  a  very  invigorating  effect  upon  the  entire  system. 
A  warm  bath  is  most  beneficial  after  severe  muscular  exertion, 
and  in  the  evening  before  retiring. 

14.  A  bath  should  not  be  taken  immediately  before  or  after 
a  full  meal  or  severe  physical  or  mental  exertion.     About  three 
hours  after  a  full  meal  the   body  is  in  the  best  condition  for 
a  bath  of  any  kind. 

15.  The   clothing   should   permit   the  utmost   freedom    of 
movement  to  all  organs  and  members  of  the  body,  and  contrib- 
ute to  the  fullest  extent  to  physical  comfort. 

16.  All  garments  worn  at  night,  as  well  as  the  bedclothes, 
should  be  thoroughly  aired  and  sunned  so  as  to  keep  them  per- 
fectly dry  and  free  from  disease  germs. 

17.  The   kidneys   are   the  most   important  organs  for  the 
excretion  of  salt,  water,  and  urea;    they  also    excrete   other 
wastes.     They  cooperate  with  the  skin  and  lungs  in  keeping 
the  blood  free  from  all  organic  waste  products.     Disease  of  any 
one  of  these  organs  throws  an  extra  amount  of  work  upon  the 
others. 

18.  Disease  of  the  kidneys  results  in  serious  impairment  of 
health.     The  skin  and  lungs  cannot  assume  the  functions  of 
the  kidneys. 

19.  Diseases  of  the  kidneys  may  be  due  to  numerous  causes, 
such  as  :  exposure  to  colds,  use  of  alcohol,  condiments,  and 
too   much  rich  food,   dislocation   of  abdominal   organs,    and 
infection  by  certain   bacteria. 


CHAPTER   XIII 

BONES   AND   JOINTS 

123.  Uses  of  Bones.  —  The  bones  of  the  human  body 
are  so  put  together  as  to  form  a  complete  human  figure 
in  size,  shape,  and  general  outline ;  they  constitute  the 
framework  of  the  body.      The  bones  form   protecting 
walls  for  some  of  the  most  delicate  organs,  as  the  brain, 
the  eye,  the  ear,  and  the  heart  and  lungs.     Muscles  are 
attached  to  bones  which  serve  as  levers  for  moving  any 
part  of  the  body  and  for   locomotion.     We  could   not 
stand,  walk,  and  run  about  if  we  had  no  bones  to  give 
strength  and  firmness  to  the  body. 

In  all  there  are  t^vo  hundred  and  six  bones  of  various 
sizes  and  shapes,  joined  together  by  strong  bands  called 
ligaments.  This  large  number  of  bones  makes  possible 
the  great  freedom  of  movement,  as  in  the  wrist,  fingers, 
ankles,  toes,  spine,  neck,  and  other  parts. 

124.  The  Skeleton.  —  The  two  hundred  and  six  bones 
of  the  body  that  together  constitute  the  skeleton  may  be 
grouped  into  three  classes :  those  of  the  head,  the  trunk, 
and  the  extremities. 

The  bones  of  the  head  may  again  be  divided  into 
those  of  the  cranium,  the  face,  and  the  ears.  In  the 
cranium,  which  is  a  firm,  thick  case  for  the  brain,  there 

167 


1 68 


HUMAN   PHYSIOLOGY 


CHAP.  XIII 


are  eight  separate  bones  very  firmly  bound  together. 
These  bones  are  as  follows  :  one  frontal,  two  parietal, 
tivo  temporal,  one  occipital,  one  etlnnoid,  and  one  spJienoid. 
You  will  find  all  but  one  in  the  diagram  below.  The 


C0/70/ 


/./Lachrymal  done 
2 

3. 


FIG.  84.  —  The  skull,  side  view. 

face  has  fourteen  bones,  all  except  the  lower  jawbone 
being  firmly  held  together  so  as  to  allow  no  movement 
to  speak  of.  The  bones  of  the  face  are  as  follows  : 
one  lower  jawbone,  two  upper  jawbones,  two  malars  or 
cheek  bones,  two  nasals  forming  the  bridge  of  the  nose, 


12 


3. 


C...J 


FlG.  85.  —  The  vertebral  column  (Huxley)  :  A,  side  view,  left  side;  Bt  back 
view;  C  1-7,  cervical  vertebrae;  D  1-12,  dorsal  vertebrae  ;  L  1-5,  lumbar 
vertebrae ;  S,  sacrum ;  C,  coccyx ;  sp  and  tr,  processes  or  projections  on 
the  vertebrae. 


HUMAN   PHYSIOLOGY 


CHAP. 


—  3 


—  10 


one  vomer  between  the  nostrils,  two  palate  bones  form- 
ing the  back  part  of  the  roof  of  the  mouth,  two  lachry- 
mal near  the  inner  angle  of  the  eyes  and  forming  part  of 
the  outer  walls  of  the  nose,  and  two  turbinated  or  scroll- 
like  bones  inside  of  the 
nose.  These  bones  form 
five  important  cavities : 
two  orbits,  two  nostrils, 
and  the  mouth.  Inside  of 
the  middle  ear  there  are 
three  small  bones :  the 
malleus,  the  stapes,  and 
the  incus. 

The  bones  of  the 
trunk  are  the  ribs  (twelve 
pairs),  the  backbone  or 
vertebra  (twenty -four  in 
all),  one  sternum  or  breast 
bone,  the  hyo id  bone  near 
the  base  of  the  tongue, 
the  pelvic  girdle,  consist- 
ing of  two  Jiip  bones  and 
the  sacrum  and  coccyx. 
Each  upper  extremity  or  arm  consists  of  the  upper 
arm,  the  forearm,  and  the  hand.  The  upper  arm  has 
three  bones :  the  scapula  or  shoulder  blade,  the  clavicle 
or  collar  bone,  and  the  humerus,  a  long,  hollow  bone  ex- 
tending from  the  elbow  to  the  shoulder.  In  the  fore- 
arm there  are  two  quite  long,  slender,  hollow  bones 
known  as  the  radius  on  the  thumb  side  and  the  ulna 


FlG.  86.  —  The  bony  walls  of  the  thorax 
(Huxley):  ab,  vertebrae;  1-12,  ribs; 
c,  sternum;  d,  cartilages  uniting  the 
ribs  and  the  sternum. 


XIII 


BONES   AND   JOINTS 


171 


on  the  little  finger  side.  In  the  hand  there  are  eight 
carpal  or  wrist  bones  arranged  in  two  rows,  five  meta- 
carpal  or  palm  bones  extending  from  the  wrist  to  the 
fingers,  and  fourteen  phalanges  in  .^ 

the  fingers. 


I 


FIG.  87.  —  The  right  humerus 
(Zuppke). 


FIG. 


3.  —  The  right  femur 
(Zuppke). 


The  lower  extremities  are  quite  like  the  upper  in  the 
number  and  general  structure  of  the  bones.  Each  leg 
consists  of  the  thigh,  the  calf  or  lower  leg,  and  the  foot. 
The  femur  or  thigh  bone  is  the  longest  and  strongest 


172  HUMAN   PHYSIOLOGY  CHAP,     n 

bone  of  the  body.     The  lower  leg  has  two  lor  er 

bones,  the  tibia  or  shin  bone,  and  the  fibula  much 
smaller  bone.  At  the  knee  there  is  a  peculiar  three- 
sided,  caplike  bone  known  as  the  patella  or  kneepan. 
The  foot  has  seven  irregular  tarsal  bones  in  the  heel  and 
ankle,  five  metatarsal  bones  in  the  instep,  and  fourteen 
phalanges  in  the  toes. 

125.    Table  of  Bones. 

BONES  OF  THE  HEAD. 

The  Cranium : 

Frontal,  in  the  forehead i 

Temporal,  in  the  temples 2 

Parietal,  at  the  sides,  and  top  of  the  head  2 

Occipital,  at  the  back  of  the  head  .  .  '  i 
Ethmoid,  sievelike  bone  between  the 

nose  and  the  brain i 

Sphenoid,  at  the  base  and  sides  in  front  i 

—  8 
The  Face : 

Inferior  maxillary,  or  lower  jawbone  .  i 

Superior  maxillary,  or  upper  jawbone  .  2 

Malar,  or  cheek  bones 2 

Nasal,  forming  bridge  of  the  nose  .  .  2 

Vomer,  partition  between  the  nostrils  .  i 
Palate,  the  back  part  of  the  roof  of  the 

mouth  and  the  sides  of  the  nose  .  .  2 
Lachrymal,  between  the  orbit  and  the 

nose 2 

Turbinated,  scroll-like  inside  of  the  nose  2 

H 
The  Two  Ears: 

Malleus,  or  hammer 2 

Incus,  or  anvil 2 

Stapes,  or  stirrup 2 

—  6 

—        28 


frortta/., 


Lotverjaw. 


Occ/p/taJ 
Vertebra 


FIG.  89.  —  The  skeleton. 


174  HUMAN   PHYSIOLOGY  CHAP. 

BONES  OF  THE  TRUNK. 

Ribs,  7  pairs  true ;  3  pairs  false ;  and  2 

pairs  floating 24 

Cervical  vertebrae  of  neck        ....  7 
Dorsal  vertebrae  of  back      .....12 

Lumbar  vertebrae  of  loins 5 

Sternum,  or  breast  bone I 

Hyoid  at  base  of  tongue i 

Hip  bone,  one  on  either  side  ....  2 

Sacrum,  below  lumbar  vertebrae   ...  i 

Coccyx,  at  end  of  vertebral  column  .     .  i 

54 
BONES  OF  THE  EXTREMITIES. 

The  Two  Upper: 

Scapula,  shoulder  blade 2 

Clavicle,  or  collar  bone 2 

Humerus,  in  upper  arm 2 

Radius,  in  forearm 2 

Ulna,  in  forearm 2 

Carpal,  in  wrist 16 

Metacarpal,  in  palm 10 

Phalanges,  in  fingers 28 

64 

The  Two  Lower : 

Femur,  or  thigh  bone 2 

Tibia,  or  shin  bone 2 

Fibula,  in  calf 2 

Patella,  at  knee 2 

Tarsal,  in  ankle    ........     14 

Metatarsal,  in  instep to 

Phalanges,  in  toes .28 

60 

124 

206 

126.  Composition  of  Bone.  —  Bones  are  made  of  hard 
and  firm  material  so  as  to  make  them  strong.  They 
contain  mineral  matter,  lime  and  potasJi  mostly.  In  the 


xin  BONES  AND   JOINTS  175 

adult  the  mineral  matter  makes  up  about  two  thirds  of 
the  entire  bone.  The  other  portion  is  animal  matter  or 
connective  tissue.  By  placing  a  small  bone  like  a 
sheep's  rib  in  a  mixture  of  one  part  muriatic  acid 
and  six  parts  water  for  two  or  three  days,  the  mineral 
matter  can  be  dissolved,  leaving  the  bone  so  soft  that 


FIG.  90.  —  A  sheep's  rib  tied  into  a  knot  after  the  mineral  matter  was  removed 
(Johnstone). 

it  may  be  tied  into  a  small  knot.  By  placing  a  bone 
in  a  fire  for  a  short  time,  the  animal  matter  can  be 
burned  away,  leaving  a  very  brittle  bone. 

In  children  the  bones  are  soft  and  may  be  easily  bent 
out  of  shape  because  they  have  a  large  amount  of  ani- 
mal matter  and  as  yet  very  little  mineral  matter.  This 
is  why  children's  bones  are  not  easily  broken.  Slowly 
the  bones  of  the  growing  person  become  hard  and 
firm  because  more  and  more  lime  displaces  the  animal 
matter  and  they  grow  strong  but  become  brittle.  In 
old  age  bones  break  easily  and  heal  slowly  when 
broken. 

127.  Structure  of  Bone.  —  Most  of  the  long  bones 
are  hollow  through  the  center.  The  cavities  are  filled 
with  soft  yellow  marrow.  This  form  of  structure  makes 
them  stronger  and  very  much  lighter  than  they  would 


I76 


HUMAN   PHYSIOLOGY 


CHAP. 


be  if  they  were  solid.    At  the  ends  a  long  bone  is  rather 
spongy,  while  the  shaft  is  very  compact  in  structure. 

Under  the  microscope  a  thin  slice  of  bone  presents 
an  interesting  appearance.     Little  canals  appear  run- 
ning in  all  directions,  and  small  lakes 
can  be  seen  throughout  the  entire  mass 
even  in  its  most  solid  parts.     Blood  and 
^          lymph   flow   through   these   canals   and 
^          permeate  the  bone  from  the  outside  to 


Marrow 
cav/ty 


Hard 


FIG.  92.  —  A  cross-section  of  bone,  highly  magnified 
(Kocher). 

its  very  center.  Bones  grow,  and  hence 
must  have  food  material  carried  to  them 
and  waste  matter  removed  from  them. 

Bone  is  covered  with  a  very  thin, 
tough  connective  tissue  membrane  called 
the  periosteum,  and  the  hollow  shaft 
of  the  long  bones  is  lined  with  a  some- 
what similar  membrane  known  as  the 
endosteum.  These  are  very  important  membranes.  They 
fit  over  the  bony  surface  very  smoothly  and  thus  serve 
to  protect  the  bone.  Muscles  can  more  easily  attach 


FIG.  91.— The  right 
femur  cut  open 
(Zuppke). 


xni  BONES  AND  JOINTS  177 

themselves  to  the  periosteum  than  to  the  smooth  bone 
itself.  The  most  important  function  of  these  mem- 
branes is  to  carry  nourishment  to  the  bone  substance 
and  to  keep  it  in  a  healthy  condition.  Blood  vessels 
and  lymphatics  pass  into  and  through  the  bone  from 

\ 

J&=-^       ~     -^&& 

Marrow 


FlG.  93. —  The  periosteum,  partially  removed  (Johnstone). 

the  periosteum  and  endosteum.  If  the  periosteum  is 
removed  from  any  part  of  a  bone,  that  portion  of  the 
bone  soon  dies  from  a  lack  of  nourishment.  If  a  bone 
is  diseased  and  a  piece  of  it  cut  out,  but  this  membrane 
left  uninjured,  it  will  form  new  bone  in  place  of  the 
old  in  a  very  short  time.  At  the  ends  of  the  bones  a 
layer  of  cartilage  takes  the  place  of  the  periosteum. 

1.  Get  a  large  bone  and  cut  it  across  and  study  its  structure  care- 
fully.    Cut  the  enlarged  end  of  a  bone  and  notice  how  its  structure 
compares  with  that  of  the  shaft. 

2.  Remove  all  the  muscle  from  a  portion  of  the  bone,  and  run 
the  point  of  a  knife  along  its  surface.     A  thin  membrane  may  be 
peeled  oft".     This  membrane  is  the  periosteum. 

3.  Examine  a  slide  of  bone,  if  possible,  under  the  microscope. 
Notice  how  numerous  the  channels  are  through  which  the  blood  is 
carried  to  all  parts  of  the  bone. 

128.  Cartilage. — That  which  we  call  the  gristle  of 
meat  is  cartilage.  It  is  really  young  bone  in  which 
there  is  as  yet  little  mineral  matter.  Cartilage  is  firm 


1 78  HUMAN   PHYSIOLOGY  CHAP. 

enough  to  retain  its  shape,  and  elastic  enough  to  spring 
back  when  bent  out  of  position.  The  ends  of  the  nose 
and  the  ears  are  examples  of  cartilage. 

Cartilage  occurs  in  all  places  in  the  body  where  a  cer- 
tain amount  of  stiffness  and  firmness  and  at  the  same 
time  pliability  and  elasticity  are  required.  Cartilage 
serves  many  uses,  such  as  to  form  the  walls  for  certain 


I! 


FIG.  94.  —  Cartilage,  highly  magnified  (Buchholz). 

organs,  as  the  larynx  and  trachea,  to  form  enlargements 
of  the  bones,  to  furnish  a  smooth  surface  at  joints,  to 
deepen  the  socket  for  certain  joints,  to  form  cushions 
between  certain  bones,  and  to  form  projecting  organs 
like  the  nose  and  ears. 

129.  Joints.  —  Wherever  two  bones  come  together 
we  have  a  joint.  At  some  joints  there  is  little  or  no 
motion,  while  at  others  there  is  great  freedom  in  both 
the  amount  and  the  direction  of  the  motion.  At  a  joint 


XIII 


BONES   AND   JOINTS 


179 


CCLfS 


the  bones  are  covered  with  a  thin  layer  of  cartilage  which 
is  very  smooth  and  well  oiled.  A  closed  sac  of  very 
thin  connective  tissue  occurs  between  the  adjacent  sur- 
faces of  some  joints.  It  secretes  the  synovial  fluid, 
which  keeps  the  surfaces 
moist  and  enables  the  bones 
to  move  with  little  friction. 

The  bones  are  held  to- 
gether by  means  of  strong 
bands  of  connective  tissue 
known  as  ligaments.  In  some 
cases  a  bone  has  a  large 
head  that  fits  into  a  deep 
socket  of  another,  as  at  the 
hip  and  shoulder,  so  that 
the  air  pressure  alone  may 
be  sufficient  to  keep  them  in  ^ 
place.  But  even  those  bones 
have  a  large  number  of  very 
strong  ligaments  as  well  as 
muscles  that  extend  from 
one  bone  to  the  other  and 
hold  them  together  very 
firmly. 

Joints  may  be  divided  into  several  classes  —  as  the 
ball-and-socket,  pivot,  hinge,  saddle,  gliding,  and  suture. 
Where  the  round  head  of  one  bone  fits  into  a  deep 
cavity  or  socket  of  another,  as  at  the  hip  and  shoulder, 
in  such  a  way  as  to  permit  rolling  motion  in  any  direc- 
tion, we  have  a  ball-and-socket  joint.  The  pivot  joint  is 


tib 


FIG.  95.  —  The  right-knee  joint.  The 
outer  half  of  the  femur  and  patella 
cut  away.  (Huxley.)  fern,  fe- 
mur ;  pat,  patella ;  tib,  tibia ; 
fib,  fibula;  caps,  capsule  of  joint; 
/,  /,  ligaments  ;  c,  cartilage ;  e, 
tendon. 


i8o 


HUMAN    PHYSIOLOGY 


CHAP. 


one  in  which  one  bone  turns  or  rotates  upon  another  as 
is  shown  in  turning  the  forearm.  In  the  hinge  joint  one 
bone  moves  upon  another  in  two  directions  only,  back 
and  forth,  like  the  blade  of  a  jackknife  or  a  door  on  its 
hinges.  The  joints  at  the  elbow,  the  knee,  the  fingers, 

and  toes  are  examples  of 
this  class.  The  saddle  joint 
is  illustrated  in  the  joint 
between  the  thumb  and  the 
wrist.  In  the  gliding  joint 
one  plane  surface  glides 
on  another,  as  the  carpal 
bones  of  the  wrist  and  the 
tarsals  of  the  ankle.  The 
bones  of  the  cranium  are 
so  dovetailed  together  as 
to  permit  of  no  real  mo- 
tion, and  such  joints  are 
known  as  sutures.  Several 
different  kinds  of  sutures 
occur  among  the  bones  of 
the  head. 


bones 


FIG.  96.  —  The  bones  of  the  wrist. 
The  outer  part  cut  away  to  show 
the  arrangement.  (From  Heitz- 
mann  by  Zuppke.) 


1.  Procure  a  sheep's  knee  and  study  the  way  the  two  bones  fit 
together  and  how  they  are  held  in  place. 

2.  Cut  the  several  ligaments  and  trace  each  in  both  directions. 

3.  Notice  the  kneepan  and  see  how  it  serves  to  protect  the  joint. 

130.  Posture. — The  bones  of  a  young  child  are  so 
soft  that  they  can  be  easily  bent  because  the  amount  of 
lime  in  them  is  small.  That  is  why  a  child  should  not 
be  encouraged  to  stand  or  walk  when  too  young.  The 


XIII 


BONES  AND   JOINTS 


181 


bones  are  too  weak  to  bear  up  the  weight  of  the  body 
and  therefore  become  bent,  resulting  in  "bowlegs." 
Every  healthy  child  will  learn  to  walk  soon  enough  if 
left  to  take  his  own  time. 

Many  young  persons  form  the  bad  habit  of  standing 
on  one   foot,   sitting  bent  over,  walking  in  a  careless, 


J 


Correct.  More  restful.  Very  improper. 

FIG.  97.  —  Postures  in  standing.     (From  Shaw's  "  School  Hygiene."  ) 

indifferent  manner,  and  sleeping  with  the  head  on  a 
thick  pillow.  By  doing  these  things  habitually  the 
growing  bones  of  the  young  become  hopelessly  deformed. 
We  all  admire  the  straight  back,  the  square  shoulders, 
the  full  chest,  and  the  graceful  gait.  They  are  the 
result  of  easy  and  natural  positions  of  the  body  in  lying, 
sitting,  standing,  and  walking. 


182 


HUMAN   PHYSIOLOGY 


CHAP. 


FlG.  98.  —  Correct  position  at  school  desk. 


The  correct,  natu- 
ral, easiest  standing 
position  demands  that 
the  feet  be  placed  as 
when  toeing  a  line, 
and  that  the  weight 
of  the  body  be  thrown 
equally  upon  the  two 
legs.  In  such  a  pos- 
ture the  trunk  is 
evenly  poised,  and  all 
parts  of  the  body  are  in 
their  natural  places. 


The  correct  sitting  posture  demands  that  the  pelvis  rests 
equally  on  the  seat, 
with  the  body  erect 
and  the  head  so  placed 
that  the  line  of  direc- 
tion falls  within  the 
line  joining  the  bones 
of  the  pelvis  resting 
on  the  seat.  This 
may  be  called  a  sym- 
metrical posture,  as  it 
is  the  easiest  to  main- 
tain for  any  length  of 


FIG.  99.  —  Desk  and  seat  too  small.     Head 
and  spine  bent,  and  legs  and  feet  cramped. 


time,    because    it   re- 
quires   the     smallest 
expenditure  of   muscle  energy,   and   leads  to  physical 
beauty  and  proper  carriage. 


XIII 


BONES  AND   JOINTS 


183 


FIG.  zoo.  —  Skull  of  a  Flathead  Indian  child 
(Zuppke). 


Often   the   clothing   may  be   the    cause  of    physical 
deformity.     Tight  bands  at  the  wrists  of  the  growing 
child   are  sure  to  re- 
sult   in    a    deformed 
bone.      Tight    lacing 
about  the  waist  when 
young     will     perma- 
nently    deform     the 
chest,     diminish     the 
capacity  of  the  lungs, 
and  push  out  of  place 
the     abdominal     and 
pelvic    organs.      The 
feet  become  tender  and  deformed  by  wearing  tight  and 
otherwise  unhygienic  shoes. 

There  is  a  tribe  of  Indians  inhabiting  the  mountains 
of  Idaho  known  as  the  "  Flatheads,"  because  they  band- 
age the  head  of  every  young  child  in  such  a  way  that  it 
becomes  permanently  long  and  flat.  The  Chinese  think 

it  fashionable  for  ladies  to  have 
small  feet.  They  secure  this 
by  tightly  bandaging  the  feet 
of  the  little  girls.  Among  the 
ignorant  and  superstitious  sav- 
age and  heathen  people  there 
may  be  some  excuse  for  thus 
deforming  the  body,  marring 
£-  its  beauty,  and  impairing  its 
vigor,  but  among  civilized  and 

FlG.  101.  —  Foot  of  a  Chinese 

woman  (Zuppke).  enlightened  nations  the  fash- 


HUMAN   PHYSIOLOGY 


CHAP. 


ionable  long,  narrow  foot,  the  high  heel,  and  the  de- 
formed waist  cannot  be  defended.  Fashion  makes  us 
do  very  strange  things  indeed. 

131.  The  Curved  Spine  and  Round  Shoulders.  —  One 
of  the  most  common  deformities  among  young  men 
and  women  is  a  curved  spine  and  round  shoulders. 
The  spine  may  bend  either  to  the  right  or  the  left,  for- 
ward or  backward.  In  some  cases  there  is  a  combina- 


Right  curve.  Left  curve.  Round  shoulders. 

FIG.  102.  —  Showing  deformed  chests.   (Drawn  by  H.  Meyer  from  photographs.) 

tion  of  two  or  more  of  these  directions.  Curvature  of 
the  spine  may  be  due  to  a  great  many  causes,  but  the 
most  common  is  improper  posture  of  the  body  on  account 
of  seats  and  desks  that  are  either  too  high  or  too  low 
or  for  some  other  reason  are  not  adapted  to  the  pupil. 
Under  such  conditions  one  shoulder  may  be  raised  above 
the  other,  causing  lateral  curvature  of  the  spine,  or  the 
body  may  be  bent  forward  as  in  reading  and  writing, 
causing  a  fold  across  the  abdomen  in  the  region  of  the 
stomach  which  curves  the  spine  backward,  displaces 


XIII 


BONES   AND   JOINTS 


185 


the  abdominal  organs,  and  compresses  some  of  the  large 
blood  vessels  so  as  to  disturb  the  action  of  the  heart. 
Just  as  harmful  is  the  slipping  forward  in  the  seat  so 
frequently  seen  in  the  schoolroom.  The  visceral  organs 
now  press  against  the  spine,  crowding  it  back  and  caus- 
ing a  curvature ;  the 
shoulders  drop  for- 
ward, causing  a  flat- 
ness and  compres- 
sion of  the  chest 
which  seriously  dis- 
turbs respiration  and 
circulation.  When 
the  seat  is  so  high 
that  the  feet  must 
dangle  in  the  air  all 
day  long  because 
they  cannot  reach 
the  floor,  the  strain 
on  the  femur  is  sufficient  to  deform  it.  The  discomfort 
and  fatigue  may  be  patiently  borne,  but  the  pupil  can- 
not do  as  good  school  work  as  he  could  under  more 
favorable  conditions.  Mental  work  depends  to  a  large 
extent  upon  physical  comfort. 

Such  improper  positions  assumed  day  after  day  for  a 
series  of  years  tend  to  fix  the  bones  of  the  spine,  chest, 
and  shoulders  and  cause  permanent  deformity.  To 
obviate  all  these  difficulties  schoolrooms  should  be 
supplied  with  single  adjustable  seats  and  desks,  and  then 
sufficient  time  taken  to  adjust  the  seat  and  desk  of  each 


FIG.  103.  —  Incorrect  position  frequently  seen 
in  the  schoolroom. 


1 86 


HUMAN   PHYSIOLOGY 


CHAP. 


FlG.  104.  —  An  adjustable  seat  and  desk.     From 
a  sketch  furnished  by  Dr.  Mosher.     (Zuppke.) 


pupil  at  least  once 
a  term.  The  seat 
and  desk  shown 
here  are  raised  and 
lowered  in  the  same 
way  as  are  revolv- 
ing office  chairs. 

Besides  being  ad- 
justable, a  good, 
comfortable  school 
desk  must  afford 
sufficient  room  for 


the  legs  and  feet  to  take  easy,  natural  positions,  so  as 
not  to  cramp  the  blood  vessels  in  any  way.     The  back 


FlG.  105.  — An  adjustable  seat  and  desk  as  used  for  writing.     From  Dr,  Mosher's 

"  Hygienic  Desks  for  School  Children,"  Educational  Review. 
FlG.  106.  —  Same  seat  and  desk  as  used  for  reading. 


xin  BONES  AND   JOINTS  187 

of  the  seat  must  be  so  constructed  that  there  is  ample 
room  to  sit  well  back  on  the  seat,  and  at  the  same  time 
it  must  furnish  a  firm  support  for  the  loins.  In  this  last 
particular  most  of  the  school  seats  are  especially  faulty. 


SUMMARY  OF  THE   MAIN   POINTS 

1.  The  bones  serve  (i)  to  form  the  framework  of  the  body, 
(2)  to  protect  certain  soft  and  delicate  organs,  and  (3)  to  form 
levers  for  the  attachment  of  muscles. 

2.  The  skeleton  consists  of  two  hundred  and  six  bones  fitted 
together  and  held  in  place  by  cartilage  and  ligaments. 

3.  Bones  consist  of  animal  and  mineral  matter.      In  early 
childhood  the  animal  matter  is  the  more  abundant,  but  it  is 
slowly  displaced  by  mineral  matter,  which  is  far  in  excess  in 
old  age. 

4.  The    long    bones    have    a    hollow   shaft    and    enlarged, 
spongy  ends.     They  are  covered  with  periosteum    and  lined 
with  endosteum,  both  of  which  are  well  supplied  with  blood 
vessels  from  which  the  bone  substance  draws  its  nourishment. 

5.  Cartilage  is  very  much  like  bone  that  contains  little  min- 
eral matter.    It  helps  to  enlarge  the  ends  of  long  bones,  and  so 
makes  better  joints,  and  to  form  the  walls  of  some  of  the  inter- 
nal organs. 

6.  A  joint  is  the  union  of  two  bones,  whether  they  move 
upon  each  other  or  not.     There  are  several  different  kinds  of 
joints,  as  ball-and-socket,  pivot,  hinge,  saddle,  gliding,  and  suture. 

7.  A  synovial  sac  occurs  between  the  bones  of  some  joints. 
It  contains  a  small  quantity  of   synovial  fluid  which  oils  the 
surfaces  to  prevent  friction. 

8.  The  bones  in  childhood  are  very  pliable  and  easily  bent 
out  of  position,  and  therefore  it  is  highly  important  always  to 
maintain  correct  postures  in  lying,  sitting,  standing,  and  walking. 


1 88  HUMAN   PHYSIOLOGY  CHAP,  xm 

9.  The  body  is  in  the  correct  standing  posture  when  the 
feet  are  placed  as  in  toeing  a  line,  and  the  weight  of  the  body 
is  thrown  equally  on  the  two  legs. 

10.  The  body  is  in  the  correct  sitting  posture  when  the  two 
bones  of  the  pelvis  rest  equally  upon  the  seat,  and  the  line  of 
direction  falls  within  the  line  joining  the  points  of  support  on 
the  seat. 

11.  Clothing  that  does  not  fit  properly  deforms  the  bones 
and  interferes  with  the  functional  activity  of  the  organs. 

12.  Two  of  the   most    serious   common  deformities  are  a 
curved  spine  and  round  shoulders.     These  deformities  com- 
press  the   thorax  and   abdomen,  and  disturb  the  respiration, 
digestion,  and  circulation. 

13.  School  desks  and  seats  are  one  cause  of  spinal  curvature 
and  round  shoulders.     Schools  should  be  furnished  with  ad- 
justable seats  and  desks. 


CHAPTER   XIV 

MUSCLES   AND   EXERCISE 

132.  Use  of  Muscles.  —  About  one  half  of  the  weight 
of  the  body  is  due  to  the  muscles,  or  lean  meat,  of  which 
it  is  composed.     Muscles  are  useful  organs,  for  without 
them  we  could  not  live  for  a  moment.     Let  us  see  what 
they  do.     Most  of  the  muscles  are  fastened  to  bones, 
which  they  completely  cover,  so  as  to  make  the  human 
form  less  angular  and  more  beautiful  in  outline.     Many 
of  the  vital  organs  of  the  body,  as  the  heart,  arteries, 
and  stomach,  are  made  almost  entirely  of  muscle  tissue. 
All  motion  of  the  body  as  a  whole,  and  of  its  various 
parts,  is  accomplished  by  the  contraction  of  the  muscles 
that  are  attached  to  bones.     Speaking  and  singing  are 
accomplished  by  very  delicately  adjusted  muscles  of  the 
chest,  throat,  and  mouth.     In  fact,  you  cannot  name  a 
single  function  of  the  body  or  of  any  of  its  parts  that 
does  not  depend  directly  or  indirectly  upon  the  action 
of  muscles. 

133.  Description  of  Muscles.  —  The  human  body  has 
Qvzrfive  hundred  muscles  which  can  be  controlled  by  the 
will,  and  a  large  number  over  which  we  appear  to  have 
no  control  whatever.     The  first  we  call   voluntary  and 
the  second  involuntary  muscles. 

189 


FIG.  107.  —  Superficial  muscles,  side  view. 


CHAP.  XIV 


MUSCLES   AND   EXERCISE 


191 


As   to    shape,   muscles  may  be  grouped  into  many 
different  classes,  known  by  separate  names  as  fusiform, 


FIG.  108.  —  Muscles  of  different  shapes  (Zuppke). 

penniform,  bipenniform,  tripennifoim,  digastric,  poly  gas- 
tric, sphincter,  etc.  The  figures  above  will  give  you 
some  idea  of  the  variety  of  shape  found  among  the 
voluntary  muscles. 


192  HUMAN   PHYSIOLOGY 

As  to  size  we  also  find  a  great  difference.  /Some  are 
very  short  and  slender,  others  are  long  ana  thick.  In 
the  ear  there  is  a  muscle  so  small  that  it  measures  about 
one  sixth  of  an  inch  in  length  and  weighs  about  a  grain, 
while  in  the  thigh  there  is  a  muscle  that  measures  over 
two  feet  in  length,  and  in  the  abdomen  there  is  a  thin, 
flat  muscle  over  twelve  inches  wide. 

A  muscle  consists  of  three  parts  :  the  beginning  or 
origin,  the  end  or  insertion,  and  the  middle  or  belly.  Some 
muscles  are  attached  to  bone  at  both  ends,  some  at  one 
end  only,  the  other  being  fastened  to  cartilage,  skin,  or 
to  another  muscle,  and  some  are  not  attached  to  bones  at 
all.  Many  of  the  muscles  taper  off  at  one  or  both  extremi- 
ties into  thin,  strong  bands  of  connective  tissue  known 
as  tendons.  When  the  fleshy  part  of  a  muscle  must  be 
far  removed  from  its  insertion,  it  has  a  very  long,  slen- 
der tendon,  as  in  the  case  of  the  muscles  that  move  the 
fingers  and  toes.  The  largest  and  strongest  tendon  of 
the  body  extends  from  the  bone  of  the  heel  up  to  the 
two  largest  muscles  of  the  calf  ;  this  is  the  tendon  of 
Achilles.  The  longest  tendon  of  the  body  extends  from 
the  heel  bone  up  to  a  small  muscle  just  back  of  the  knee. 

1.  Procure  the  lower  part  of  a  sheep's  leg  with  the  lean  meat  and 
the  hoof  on.    Dissect  out  as  many  of  the  muscles  as   you  can,  tracing 
each  in  both  directions.    Find  the  origin,  insertion,  and  belly  of  each 
muscle. 

2.  If  the  parts  are  placed  in  diluted  alcohol  for  a  few  days  they 
will  harden  somewhat  and  remain  separate. 

134.  Structure  of  Muscles.  —  We  are  all  familiar  with 
the  appearance  and  general  structure  of  muscles  as 


xiv  MUSCLES  AND   EXERCISE  193 

seen  in  beefsteak,  corned  beef,  dried  beef,  lean  mutton, 
boiled  chicken,  etc.  When  carefully  examined,  a  piece 
of  dark  meat  of  the  chicken,  or  corned  beef,  that  has  been 
"  boiled  to  rags,"  shows  many  bundles  of  fleshy  threads 
known  as  fibers,  closely 
packed  together  and 
held  in  place  by  a  very 
thin  sheath.  Each  fiber 
when  "teased  out"  with 
a  fine  needle  will  be 
found  to  consist  of  still 
smaller  threads  of  flesh 

FiG.  109.  —  Showing  several  bundles  of 

Called  fibrtlS.       A  Single  muscle  fibers  cut   across.    /  /  single 

fibril,     mUSCle     fiber,     Or  bundles.     (From  Huxley.) 

muscle  cell,  is  covered  with  a  very  delicate  membrane 
inclosing  a  soft  semifluid  substance  known  as  myosin. 

The  involuntary  muscle  differs  from  the  voluntary  in 
that  it  is  plain  instead  of  striped,  has  few  capillaries  and 
therefore  less  color,  and  is  sluggish  in  its  action. 

135.  How  Muscles  Work.  —  A  muscle  cell  has  the 
power  to  contract,  or  to  become  shorter  and  thicker 
under  the  influence  of  a  stimulus.  It  changes  its  shape, 
but  not  its  bulk.  Since  the  muscle  cells  are  placed  side 
by  side  to  form  the  thickness  of  a  muscle,  and  end  to 
end  to  form  its  length,  it  follows  that  the  muscle  as  a 
whole  grows  shorter  and  thicker  when  its  fibers  contract. 
The  longer  a  muscle,  the  greater  the  amount  of  contrac- 
tion possible. 

A  muscle  will  not  act  unless  it  is  stimulated  in  some 
way.  Each  muscle  cell  has  a  little  nerve  fiber  going  to 


194  HUMAN   PHYSIOLOGY  CHAP. 

it.  Over  this  nerve  a  message  may  be  sent  from  the 
brain,  causing  the  muscle  to  contract.  We  can  make  a 
muscle  do  just  what  we  please  if  we  have  learned  how 
to  stimulate  it. 

When  a  muscle  contracts  it  pulls  its  ends  nearer 
together ;  it  gets  shorter  and  causes  motion  in  the  part 
to  which  it  is  fastened.  We  say  the  muscle  does  work. 
In  some  way  the  heat  obtained  from  the  oxidation  of 
foods  in  the  muscle  cells  is  transformed  into  mechanical 
energy  and  used  in  doing  work.  The  thicker  a  muscle 
the  greater  the  load  it  can  move. 

In  every  contraction  a  muscle  consumes  a  certain 
amount  of  food  material,  causes  the  cells  to  break  down 
somewhat,  and  produces  waste  products.  The  muscle 
cells  must  be  repaired,  and  new  energy  must  be  stored 
up  for  future  use.  To  accomplish  this  more  food  must 
get  into  the  blood  and  be  carried  to  the  cells.  Working 
gives  us  an  appetite,  and  we  now  see  the  reason  for  it. 

A  muscle  cannot  remain  strongly  contracted  for  a 
long  time  without  becoming  tired.  It  is  difficult  to 
stand  perfectly  still  in  one  position,  to  hold  the  arm 
straight  out,  or  to  look  steadily  at  a  quiet  object.  A 
contraction  must  be  followed  by  a  relaxation.  The 
muscles  are  generally  arranged  in  pairs  so  that  when 
one  contracts  the  other  relaxes  ;  when  one  works  the 
other  rests.  The  muscle  used  in  bending  the  arm  can- 
not straighten  it,  but  another  must  be  called  into  action. 

1.  By  means  of  a  tapeline,  measure  the  muscles  of  the  right  arm 
(i)  when  extended,  and  (2)  when  flexed. 

2.  Measure  the  left  biceps  in  the  same  way. 

3.  Measure  other  large  muscles  of  the  body. 


xiv  MUSCLES  AND   EXERCISE  195 

136.   Large  Muscles. 
I.   MUSCLES  OF  THE  HEAD. 

1.  Occipito-fron tails,  moves  the  scalp  and  eyebrows,  and 

throws  the  forehead  into  transverse  wrinkles. 

2.  Orbicularis  palpebrarum,  moves  the  eyelids  and  closes 

the  eye. 

3.  Corrugator  supercilii,  used  in  frowning. 

4.  Levator  palpebrae,  opens  the  eye. 

5.  The  recti,  the  four  straight  muscles  of  the  eyeball. 

6.  Orbicularis  oris,  closes  the  mouth. 

7.  Buccinator,    compresses    the    cheeks,   and    is   used   in 

mastication. 

8.  Risorius,  draws  up  the  angles  of  the  mouth  as  in  smiling. 

9.  Temporal,  or  muscle  of  the  temple,  raises    the   lower 

jaw. 
10.  Masseter,  or  chewing  muscle,  raises  the  lower  jaw. 

II.   MUSCLES  OF  THE  NECK. 

n.  Platysma  myoides,  draws  down  the  lower  lip  and  the 
angles  of  the  mouth. 

12.  Sterno-cleido-mastoid,  depresses  the  head  and  neck  upon 

the  chest. 

13.  Scaleni  muscles,  elevate  the  ribs  in  breathing. 

III.   MUSCLES  OF  THE  TRUNK. 

14.  Trape2ius,  draws  the  head  backward,  and  elevates  the 

shoulder. 

15.  Latissimus  dorsi,  draws  the  arm  backward  as  in  chop- 

ping or  in  striking  down. 

1 6.  Rhomboideus,  draws  the  shoulder  back. 

17.  Erector  spinae,  holds  the  spine  erect. 

1 8.  Intercostals,  move  the  ribs  in  breathing. 

19.  Diaphragm,  used  in  breathing. 

20.  External  oblique     •)  These  muscles   form  the  walls    of 

21.  Internal  oblique  the  abdomen,  pull  the  trunk  for- 

22.  Transversalis  ward,  and  compress  the  abdomi- 

23.  Rectus  abclominis  J      nal  organs. 


FIG.  no.  —  Superficial  muscles,  front  view.     (From  Blaisdell's  "  Health  and 
Life."     Ginn  &  Co.) 


CHAP,  xiv  MUSCLES  AND    EXERCISE  197 

IV.   MUSCLES  OF  THE  UPPER  EXTREMITIES. 

24.  Pectoralis,  draws  the  arm  forward  and  brings  it  across 

the  chest. 

25.  Deltoid,  raises  the  arm  at  right  angles  to  the  trunk. 

26.  Serratus  magnus,  moves  the  shoulder  forward  and  upward. 

With  the  trapezius  it  is  used  in  supporting  a  weight  on 
the  shoulder  and  in  pushing. 

27.  Teres  major,  aids  in  rotating  and  drawing  the  arm  down- 

ward and  backward. 

28.  Biceps,  bends  the  arm  at  the  elbow. 

29.  Triceps,  straightens  the  arm  at  the  elbow. 

30.  The  flexors  and  extensors,  move  the  hand,  wrist,  and 

fingers. 


V.   MUSCLES  OF  THE  LOWER  EXTREMITIES. 

,   .  i       i  •  ,    •  T     •  , 

pelvis,  rotate  the  thigh  inward,  and  aid 

r 


These   muscles   bend   the  thigh  upon  the 
Iliacus 


35.  Gracilis 

36.  Gluteus 


33-  Pectmeus 

in  holding  the  body  erect. 
34.  Adductors 


These  muscles  straighten  the  thigh  at  the 
pelvis,  rotate  the  leg,  and  aid  in  standing 


37.  Biceps        j      erect. 

38.  Sartorius,  flexes  the  thigh  upon  the  pelvis  and  rotates 

the  thigh  outward. 

39.  Quadriceps,  straightens  the  leg  at  the  knee,  and  aids  in 

stooping  and  standing. 

40.  Gastrocnemius   ^ 

41.  Tibialis  j  These  muscles  aid  in  flexing  and  ex- 

42.  Peroneus  tending    the    foot,  in   bending  the 

43.  Soleus  I      knee,  and  are  used  in  standing,  walk- 

44.  Extensors  ing,  and  running. 

45.  Flexors 

The  hand  and  foot  have  numerous  small  muscles 
which  make  a  great  variety  of  movements  possible  in 
the  fingers  and  toes.  The  hand  alone  has  over  thirty 
muscles  and  the  foot  nearly  as  many. 


198  HUMAN   PHYSIOLOGY  CHAP. 

137.  Food  of  Muscles.  —  Muscle  cells  become  worn 
out  by  use.  To  keep  them  in  good  working  order  it  is 
necessary  to  supply  them  with  an  abundance  of  nutri- 
tious food  and  oxygen.  The  proteids,  you  remember,  are 
the  building  foods  and  are  necessary  to  repair  the  cells 
after  every  contraction.  The  blood  should  always  con- 
tain a  sufficient  amount  of  this  class  of  food  stuffs.  A 
person  who  does  much  muscular  work  must  eat  meats, 
cheese,  eggs,  or  other  articles  containing  proteids.  The 
heat  and  energy  used  by  a  working  muscle  can  be 
obtained  more  easily  from  carbohydrates  and  fats  than 
from  proteids.  There  should  be  an  adequate  supply  of 
these  foods  in  order  that  the  muscles  may  do  their  work 
with  the  greatest  ease  and  economy.  Water  and  salt 
are  essential  to  the  health  and  proper  activity  of  muscle 
cells. 

A  sufficient  amount  of  pure  fresh  air  to  oxidize  the 
different  foods  in  the  muscles  is  of  the  utmost  impor- 
tance. If  there  is  a  lack  of  oxygen,  the  foods  cannot 
easily  be  burned,  and  consequently  there  is  a  lack  of 
heat  and  energy  for  the  muscles  to  work  properly,  al- 
though there  may  be  an  abundance  of  food.  The  foods 
are  at  best  only  partially  oxidized  and  so  do  not  furnish 
as  much  heat  as  they  should.  And  besides  that,  the 
wastes  formed  under  such  conditions  are  very  poisonous, 
and  difficult  to  remove  from  the  blood. 

The  blood  should  contain  all  the  different  food  stuffs 
in  the  right  proportions,  and  an  adequate  supply  of 
oxygen.  The  activity  of  the  muscles  depends  upon  the 
foods  we  eat  and  the  air  we  breathe. 


xiv  MUSCLES   AND   EXERCISE  199 

138.  Value  of  Exercise.  —  Next  in  importance  to  the 
quality  and  quantity  of  foods  and  air  for  keeping  the 
muscles  in  a  healthy  condition,  is  the  matter  of  exercise. 
The  blacksmith  has  a  large,  strong  right  arm  because 
he  uses  it  so  much.  The  muscles  of  the  athlete  grow 
strong  because  of  constant  exercise.  A  muscle  that  is 
not  used  becomes  soft,  flabby,  and  feeble. 

Regular  daily  exercise  of  the  muscles  increases  the 
action  of  the  heart  and  lungs.  More  blood  containing 
food  and  oxygen  is  pumped  to  all  the  organs  of  the 
body.  The  muscles  used  most  reap  the  greatest 
benefit.  Proper  exercise  is  beneficial  to  both  old 
and  young.  The  young,  growing  person  requires  a 
greater  amount  of  exercise  than  the  adult.  As  long 
as  a  muscle  is  growing,  exercise  will  tend  to  make  it 
grow  larger  and  to  develop  it  better.  That  is  why 
those  who  get  a  great  deal  of  outdoor  exercise  look 
healthier  and  are  better  developed  physically  than 
those  who  live  indoors  most  of  the  time.  Exercise 
and  sunshine  make  people  well  and  strong. 

Muscular  exercise  has  a  wholesome  influence  upon 
all  the  organs  of  the  body.  The  digestive  apparatus 
grows  stronger;  therefore  more  foods  are  eaten  and 
they  are  better  digested.  The  heart  and  lungs  grow 
stronger  and  are  able  to  do  their  work  better.  The 
lymphatics  perform  their  functions  of  draining  the 
wastes  from  the  cells  with  greater  efficiency.  The 
skin,  liver,  and  kidneys  remove  the  waste  materials 
from  the  blood  more  easily.  The  brain  gets  a  larger 
amount  of  nourishment  and  the  mind  is  clearer  and 


200  HUMAN   PHYSIOLOGY  CHAP. 

more  vigorous.  The  happiness,  vigor,  and  usefulness 
of  a  person  depend  so  largely  upon  his  physical  con- 
dition that  it  becomes  a  moral  obligation  to  take  proper 
exercise  every  day. 

139.  Amount  of  Exercise.  —  The  amount  of  exercise 
a  person  should  take  depends  upon  his  age,  occupa- 
tion, and  general  health.  Very  young  children  will 
take  a  sufficient  amount  of  exercise  if  they  are  well 
and  have  an  opportunity  to  move  about  freely,  but 
often  they  are  carried  too  much,  and  dressed  in  tight, 
heavy  clothing.  Nothing  is  better  to  make  the  baby 
well  and  strong  than  to  strip  off  all  its  clothes  and  give 
it  an  opportunity  to  kick  a  few  minutes  daily  on  the 
floor,  in  a  warm,  sunny,  well-ventilated  room.  A  little 
later  the  child  should  be  encouraged  to  walk,  run,  and 
play  outdoors  every  day.  The  many  natural  sports  and 
games  of  children  are  far  better  at  this  time  than 
any  artificial  system  of  physical  culture.  The  common 
games  and  sports,  like  drop-the-handkerchief,  rolling- 
the-hoop,  leapfrog,  hare  and  hound,  cycling,  baseball, 
horseback  riding,  basket-ball,  croquet,  golf,  fishing,  ten- 
nis, rowing,  and  swimming  are  among  the  most  healthful 
kinds  of  exercise  for  both  boys  and  girls.  Many  of 
them  are  equally  valuable  for  men  and  women. 

Physical  exercise  taken  in  the  gymnasium  is  usually 
less  beneficial,  because  it  so  often  is  an  irksome  task 
in  which  the  person  feels  no  real  pleasure,  but  simply 
does  it  for  his  health.  The  change  of  scene,  the  pleas- 
urable state  of  mind,  the  agreeable  companions,  tend  to 
increase  the  value  of  any  exercise. 


xiv  MUSCLES   AND   EXERCISE  201 

Too  much  exercise  is  just  as  harmful  as  too  little. 
Overwork  is  likely  to  cause  the  heart  to  dilate  and  its 
valves  to  weaken,  the  arteries  to  enlarge,  and  the  re- 
spiratory organs  to  become  diseased.  Excessive  exer- 
cise is  always  followed  by  great  fatigue.  The  question 
of  how  much  exercise  to  take  must  be  solved  by  each 
person  for  himself. 

140.  Physical  Training  in  our  Schools.  —  No  system 
of  physical  culture  can  take  the  place  of  the  outdoor 
games  and  sports  of  which  children  are  so  fond.  But 
the  chief  benefit  of  systematic  exercise  in  the  schools 
lies  in  the  fact  that  it  tends  to  a  harmonious  develop- 
ment of  all  the  muscles  of  the  body  under  the  perfect 
control  of  the  will.  Baron  Posse,  a  great  leader  in  edu- 
cational gymnastics,  says,  "  It  is  not  to  produce  great 
bulk  of  muscle,  but  to  cause  that  already  present  to 
respond  readily  to  volition ;  to  improve  the  functional 
activity  of  the  body ;  and  to  counteract  and  correct 
tendencies  to  abnormal  development,  especially  those 
resulting  from  the  artificial  life  of  civilization."  In  any 
well-graded  system  of  physical  exercise  the  movements 
are  so  varied  and  numerous  that  no  muscle,  large  or 
small,  escapes  its  share  of  exercise.  In  the  games  and 
sports  a  few  muscles  get  most  of  the  exercise,  while, 
some  are  not  used  at  all.  In  the  gymnasium  an  attempt 
is  made  to  exercise  the  weak  and  neglected  muscles, 
so  as  to  develop  them  in  harmony  with  the  rest;  and 
to  bring  about  a  perfect  control  of  every  muscle,  and 
economy,  grace,  and  freedom  in  all  the  movements  of 
the  body. 


202  HUMAN   PHYSIOLOGY  CHAP. 

The  simple  exercises  of  any  system  can  be  given  in 
the  regular  class  room  if  necessary,  without  apparatus 
or  music.  During  the  gymnastic  period  the  room  should 
be  well  ventilated,  so  that  an  abundance  of  pure  air  may 
be  carried  to  all  the  organs  of  the  body.  The  exercise 
should  be  pleasant  and  short,  but  sharp  and  vigorous, 
otherwise  it  will  be  of  little  value. 

141.  Time  of   Exercise.  —  Exercise    should  be  taken 
regularly  every  day,  so    that   the  body  becomes   used 
to  it  and   does    not   feel    fatigue  too    easily.     A  small 
amount  of  moderate  exercise  taken  every  day  is  more 
beneficial  than  a  greater  amount  once  a  week.     If  the 
exercise  is  regular,  a  little  more  may  be  taken  each  suc- 
ceeding day  until  the  muscles  become  hard  and  strong, 
so  that  it  is  almost  impossible  to  fatigue  them. 

Moderate  exercise  can  be  safely  taken  any  time  of 
day  except  immediately  after  a  full  meal.  At  such  a 
time  a  large  amount  of  blood  is  needed  in  the  stomach 
and  intestines,  and  if  drained  off  to  the  muscles  the 
foods  will  not  be  properly  digested  and  absorbed.  The 
best  time  for  severe  physical  exertion  is  about  two  hours 
after  a  meal.  The  exercise  indulged  in  after  supper 
should  be  rather  light. 

142.  Fatigue  and  Rest. : —  The  fatigue  of  a  muscle  is 
due  to  two  causes.     The  food  supply  in  the  muscle  and 
in  the  blood  is  used  up,  and  the  cells  become  fatigued 
from   a   lack    of   nourishment.     The   second    cause   of 
fatigue  is  the  formation  of  certain  waste  products  by 
the   action  of   the  muscles,  and  their   accumulation  in 
the  cells  and  lymph.     The  muscular  stiffness  and  sore- 


xiv  MUSCLES  AND   EXERCISE  203 

ness  that  follow  severe  exercise  when  one  is  not  used 
to  it,  .come  from  the  presence  of  a  large  amount  of  such 
poisonous  wastes. 

Rest  and  sleep  give  time  for  the  removal  of  all  these 
wastes.  The  cells  may  also  be  repaired  by  the  proteid 
foods  and  stored  with  material  for  future  use.  If  the 
exercise  has  been  very  severe,  the  wastes  may  poison 
the  cells  of  the  muscles  so  that  they  do  not  recover 
fully  for  several  days.  During  perfect  rest  and  in  sleep 
the  muscular  activity  is  at  its  lowest  point,  and  these 
reparative  and  recuperative  processes  are  carried  on 
most  effectively. 

143.  Massage.  —  As  understood  and  practiced  at  pres- 
ent massage  means  a  systematic  stroking,  rubbing,  tap- 
ping, pressing,  or  kneading  of  the  skin  and  muscles  by 
a  person  trained  in  this  art.  Each  process  is  subject  to  a 
great  variety  of  modifications,  and  may  be  either  gentle 
or  vigorous.  It  is  now  used  as  a  mode  of  treatment  in 
many  different  bodily  disorders.  It  is  extensively 
employed  in  certain  nervous  diseases,  especially  in 
those  that  require  prolonged  bodily  rest. 

Massage  may  take  the  place  of  exercise  when  per- 
sons are  sick  or  too  weak  to  endure  physical  exertion. 
The  value  of  massage  lies  in  the  fact  that  by  vigorous 
mechanical  means  poisonous  wastes  are  pressed  out 
of  the  tissues,  lymph  flow  is  stimulated,  circulation  is 
increased,  muscle  cells  are  excited  to  greater  activity, 
and  all  the  tissues  of  the  body  are  made  to  function 
better.  Nothing  will  set  up  the  circulation  and  remove 
the  waste  products  in  a  bruise  quicker  than  good  vigor- 


204  HUMAN   PHYSIOLOGY  CHAP. 

ous  rubbing  with  the  hands.  A  good  vigorous  rubbing 
of  the  entire  body  with  the  hands  or  with  a  rough,  dry 
towel  is  an  excellent  form  of  exercise  for  anybody. 

144.  Alcohol  and  Tobacco.  —  It  is  a  fact  of  common 
observation  that  alcohol  acts  upon  the  nerves  in  such  a 
way  as  to  make  it  difficult  and  impossible  to  control 
the  muscles.  The  unsteady  and  staggering  gait  of 
the  drunkard  is  an  illustration.  The  young  men  on  the 
baseball,  football,  track  teams,  and  rowing  crews  in 
the  best  universities  of  this  country  are  not  allowed 
to  drink  alcoholic  beverages  of  any  kind,  or  to  smoke 
cigars  or  cigarettes  at  any  time.  The  reason  for  this  is 
apparent. 

The  effect  of  stimulants  and  narcotics  is  most  marked 
upon  the  nervous  system.  They  act  upon  the  muscles 
chiefly  in  an  indirect  way.  But  the  presence  of  these 
drugs  in  the  blood  may  affect  the  nutrition  of  the  mus- 
cles, causing  them  to  become  weak  and  flabby,  and  there- 
fore sluggish  and  irresponsive  to  all  commands  sent  to 
them  over  the  nerves.  They  lose  their  natural  strength 
and  power  of  endurance. 

SUMMARY  OF  THE   MAIN   POINTS 

i.  The  muscles  cover  the  bony  framework,  making  the  form 
round  and  full,  cause  all  movements,  and  form  walls  for  some 
important  organs. 

'2.  There  are  about  five  hundred  voluntary  muscles  in  the 
body  and  a  large  number  of  involuntary  muscles.  Muscles 
differ  widely  in  size  and  shape. 

3.    A  muscle  has  an  origin,  an  insertion,  and  a  fleshy  part 


xiv  MUSCLES   AND    EXERCISE  205 

called  the  belly.     At  one  or  both  ends  of  some  muscles  we 
find  a  strong,  thin  band  of  connective  tissue  called  a  tendon. 

4.  A  muscle  is  made  of  bundles  of  fibers  held  together  by  a 
thin  sheath  of  connective  tissue.    A  fiber  consists  of  still  smaller 
threads  called  fibrils  or  muscle  cells. 

5.  The  muscle  cells  are  arranged  side  by  side  to  form  the 
thickness  of  a  muscle,  and  end  to  end  to  form  its  length. 

6.  All  muscles  are  well  supplied  with  blood  vessels,  nerves, 
and  lymphatics.     They  are  well-nourished  organs. 

7.  When  a  muscle  contracts  it  changes  its  shape  without 
altering  its  bulk.     It  becomes  shorter  and  thicker  because  each 
muscle  cell  has  the  peculiar  power  to  change  its  form  in  that 
way. 

8.  A  muscle  cannot  remain  contracted  very  long  without 
becoming  fatigued.     It  uses  up  food  material  and  produces 
waste  matter. 

9.  Most  of  the  voluntary  muscles  are  arranged  in  pairs,  so 
that  one  bends  a  limb  and  the  other  straightens  it. 

10.  In  order  to  keep  the   muscles  in  a  healthy  condition, 
they  must  have  an  abundant  supply  of  wholesome  foods,  pure 
air,  and  proper  exercise  and  rest  at  regular  intervals. 

11.  Proper  exercise  in  which  a  person  takes  a  lively  interest 
improves  the  nutrition  of  all  the  organs  of  the  body,  and  there- 
fore conduces  to  health  and  vigor. 

12.  Over-exercise  enlarges  the  walls  of  the  heart  and  arter- 
ies, impairs  the  cardiac  valves,  injures  the  respiratory  organs 
and  the  brain,  and  is  followed  by  excessive  fatigue. 

13.  Physical  training  tends   to  a   harmonious   development 
and  a  perfect  control  of  all  the  muscles  of  the  body.     It  gives 
grace  in  carriage  and  ease  in  movement,  and  may  be  employed 
to  develop  the  weak  or  neglected  muscles. 

14.  Exercise  should  not  t>e  taken  just  before  or  immediately 
after  a  full  meal.     Moderate  daily  exercise  should  be  taken  by 
all. 


206  HUMAN   PHYSIOLOGY  CHAP,  xiv 

15.  After  exercise  muscles  need  rest  and  sleep,  so  that  the 
wastes  may  be  removed  and  the  cells  repaired  and  stored  with 
energy-producing  food  materials. 

1 6.  Stimulants  and  narcotics  make  the  muscles  weak  and 
flabby  because  of  impaired  nutrition.     They  become  sluggish 
and  do  not  respond  to  ordinary  stimuli. 


CHAPTER   XV 

SPECIAL   USES   OF   MUSCLES 

145.  Review.  —  In   the    last   two    chapters  we    have 
learned   that   the  bones  are   so   joined   together  as  to 
permit   freedom    of   movement  in   various    ways ;    that 
there  are  ball-and-socket,  pivot,  hinge,  saddle,  and  glid- 
ing joints,  all  of  which  allow  more  or  less  movement  of 
the  bones ;  and  that  most  of  the  voluntary  muscles  are 
fastened  to  bones.     These  muscles  are  called    skeletal 
muscles.     The  contraction  of  a  skeletal  muscle  always 
causes  some  bone  to  move.     It   is   the    action    of   the 
muscles  upon  the  bones  that  gives  rise  to  motion  of  any 
part  of  the  body  and  to  movement  of   the  body  as  a 
whole. 

Standing,  walking,  running,  swimming,  gesturing, 
speaking,  whispering,  and  singing  are  each  accomplished 
by  the  action  of  different  groups  of  muscles  stimulated 
in  a  definite  order.  In  this  chapter  we  shall  learn 
something  about  these  special  functions  of  the  muscles. 

146.  Bones  as  Levers. — When  a  strong   stick   or  a 
crowbar  is  used  to  move  a  heavy  load,  as  in  prying  a 
stone  out  of  the  ground,  it  becomes  a  lever.     There  are 
three  classes  of  simple  levers  in  common  use.    They  are 
known  as  levers  of  the  first,  second,  and  third  class.     In 

207 


208  HUMAN   PHYSIOLOGY  CHAP. 

prying  up  a  stone  by  bearing  down  on  one  end  of  the 
crowbar,  it  becomes  a  lever  of  the  first  class ;  the  power 
is  at  one  end,  the  load  at  the  other,  and  the  fulcrum 


Fu/cram  Power 

i 

First  C/ass. 


\ 


Power 


Weight 

3ecor?af 


\ 


_  .  Power 

Fu/crum 


Third  C/ass. 

FIG.  in.  —  Showing  the  three  classes  of  levers  (Zuppke). 

somewhere  between  the  two.  If  one  end  of  the  crow- 
bar is  under  the  stone  and  an  attempt  is  made  to  lift  it 
by  pulling  up  on  the  other  end,  it  is  used  as  a  lever  of 
the  second  class ;  the  power  is  at  one  end,  the  fulcrum 


xv  SPECIAL  USES  OF   MUSCLES  209 

at  the  other,  and  the  load  somewhere  between  the  two. 
When  the  load  is  at  one  end,  the  fulcrum  at  the  other, 
and  the  power  between  the  two,  the  lever  is  of  the  third 
class. 

All  these  levers  are  illustrated  in  the  human  body  in 
the  arrangement  of  the  bones  and  muscles.  The  bones 
correspond  to  the  crowbar ;  they  are  the  levers ;  the 
contracting  muscles  attached  to  them  furnish  the  power ; 
and  the  body  as  a  whole,  any  of  its  parts,  or  any  object 
moved,  serves  as  the  load. 


FIG.  112.  —  The  bones  of  the  arm,  showing  the  biceps  muscle  and  its  tendons 
at  a  and  P.  The  action  of  the  biceps  illustrates  a  lever  of  the  third  class,  P, 
power,  F,  fulcrum,  and  W,  weight.  (Huxley.) 

When  a  weight  is  lifted  by  bending  the  arm  at  the 
elbow,  the  radius  and  ulna  constitute  the  lever,  the 
object  on  the  hand  the  load,  the  elbow  the  fulcrum, 
and  the  muscles  of  the  upper  arm  (biceps)  the  power. 
The  muscles  are  attached  to  the  bones  a  short  distance 
below  the  elbow,  so  that  the  power  is  applied  between 
the  load  and  the  fulcrum.  Here  we  have  a  lever  of  the 
third  class.  In  raising  the  body  on  tiptoe,  the  tarsal, 


210 


HUMAN   PHYSIOLOGY 


CHAP. 


metatarsal,  and  phalanges  together  constitute  the  lever. 

The  phalanges  constitute  the  fulcrum  ;  the  muscles  of 

the  calf,  attached  to  the  heel 
bone  by  the  tendon  of  Achil- 
les, furnish  the  power ;  and  the 
weight  of  the  body  resting  upon 
the  ankle  is  the  load.  This  illus- 
trates a  lever  of  the  second 
class.  In  a  similar  way  every 
muscular  movement  can  be 
shown  to  fulfill  the  conditions 
of  one  or  more  of  these  levers. 
147.  Standing.  —  When  lying 
on  the  back  perfectly  quiet,  with 
every  muscle  relaxed,  as  in  sound 
sleep,  the  skeletal  muscles  are 
doing  no  work.  An  infant  can- 
not stand  at  birth,  and  yet  its 
muscles  may  be  used  in  kicking 
and  throwing  the  arms  about. 
It  is  only  after  the  bones  have 
gained  sufficient  strength,  and 
the  muscles  have  come  under 
the  control  of  the  will,  that  the 
child  can  assume  the  erect  pos- 
ture. 

Standing  involves  the  use  of 
many  muscles  and  nerves.  But 
after  we  have  learned  to  stand, 
these  nerves  stimulate  the  vari- 


FlG.  113.  —  Showing  the  at- 
tachment of  the  most  im- 
portant muscles  used  in 
standing.  The  muscles  at 
I,  II,  and  III  tend  to  keep 
the  body  from  falling  for- 
ward; and  those  at  i,  2,  3, 
4,  and  5  tend  to  keep  it 
from  falling  backward.  The 
arrows  indicate  the  direc- 
tion in  which  the  muscles 
pull.  (Huxley.) 


xv  SPECIAL   USES   OF   MUSCLES  211 

ous  muscles  so  that  they  act  correctly  without  any 
attention  on  our  part.  The  muscles  of  the  calf,  knee, 
trunk,  back,  and  neck,  and  many  others,  all  work  to- 
gether in  holding  the  body  erect. 

Sitting  differs  from  standing  in  that  the  point  of  sup- 
port is  changed  from  the  feet  to  the  bones  of  the  pelvis. 
The  muscles  of  the  legs  are  not  active  as  they  are  in 
standing,  but  the  same  muscles  of  the  trunk,  back,  and 
neck  are  employed  as  in-  standing. 

The  part  the  nerves  play  in  standing  and  sitting  can 
be  best  shown  when  a  person  becomes  unconscious,  as 
in  fainting.  He  falls  to  the  ground  perfectly  helpless, 
although  the  bones  and  muscles  are  not  injured  in  any 
way.  The  brain  sends  no  stimuli  to  the  muscles,  and 
they  cease  to  act.  The  muscles,  when  in  good  condi- 
tion, are  the  obedient  servants  of  the  brain,  and  respond 
to  the  slightest  stimulation,  but  as  soon  as  the  brain 
does  not  stimulate  them  they  relax,  and  wait  for  further 
orders. 

148.  Walking  and  Running.  —  In  standing,  both  feet 
rest  on  the  ground  all  the  time ;  but  in  walking,  part  of 
the  time  both  feet  touch  the  ground,  then  the  right  only 
while  the  left  swings  forward,  next  the  left  while  the 
right  swings.  The  foot  that  is  on  the  ground  gives 
the  body  a  slight  push  forward  which  would  send  it 
headlong  to  the  ground  if  it  were  not  checked  by 
placing  the  other  foot  forward  in  time. 

Walking  seems  to  be  an  act  of  falling  forward  and 
catching  one's  self.  This  is  accomplished  by  the  use  of 
a  large  number  of  muscles.  Even  the  muscles  of  the 


212  HUMAN   PHYSIOLOGY  CHAP. 

arms,  which  are  least  concerned,  aid  somewhat  in  bal- 
ancing the  body.  You  will  observe  that  the  arm  and 
leg  on  the  same  side  swing  in  opposite  directions.  The 
fact  that  so  many  of  the  large  muscles  are  employed  in 
walking  makes  it  one  of  the  most  beneficial  forms  of 
exercise. 

In  running,  both  feet  never  touch  the  ground  at  the 
same  time,  but  both  are  in  the  air  for  a  short  period  in 
each  leap.  The  foot,  as  it  leaves  the  ground,  gives  the 
body  a  much  stronger  push  forward  than  in  walking, 
and  the  body  is  inclined  much  more.  Running  is  a 
valuable  form  of  exercise,  as  it  involves  so  many  of 
the  large  muscles.  One  must  be  careful,  however,  to 
breathe  properly,  and  not  to  continue  such  severe  exer- 
cise too  long. 

In  leaping,  both  feet  leave  the  ground  at  the  same 
time  and  are  used  in  throwing  the  body  forward.  It  is 
an  excellent  exercise  for  the  young.  Swimming  is  a 
mode  of  moving  the  body  along  in  the  water  by  the 
combined  action  of  the  muscles  of  the  arms  and  legs. 
No  form  of  exercise  brings  into  use  a  larger  number  of 
muscles,  or  is  better  to  give  us  general  bodily  strength 
than  swimming. 

149.  Muscles  of  Expression.  —  Muscles  of  the  face 
and  other  parts  of  the  body  are  used  to  indicate  feel- 
ings of  pleasure,  pain,  sorrow,  confidence,  anger,  fear, 
etc.  The  facial  muscles  are  all  flat,  and  attached  to  the 
skin  in  such  a  way  as  to  cause  the  mouth  and  eyes  to 
take  a  great  variety  of  positions  when  they  contract. 

The  muscles  of  expression  may  be  trained  by  a  little 


XV 


SPECIAL  USES   OF   MUSCLES 


213 


effort   so   as  to   give  the  countenance   a   pleasant  ap- 
pearance. 

150.  The  Larynx  and  its  Use.  —  In  studying  the  air 
passages  we  learned  something  about  this  organ,  called 
the  voice  box.  The  larynx  is' made  up  of  nine  separate 
pieces  of  cartilage  held  together  by  connective  tissue 
and  a  number  of  delicate  muscles.  At  the  lower  end 


fpigloUfs 


FIG.  114.  —  The  larynx,  top  view  (Zuppke)  :  A  and  a,  the  vocal  cords  in  resting 
position ;  B  and  b,  the  vocal  cords  in  position  for  producing  voice. 

the  larynx  is  attached  to  the  trachea  by  means  of  the 
large  cricoid  cartilage  which  has  the  shape  of  a  signet 
ring.  Above  this  is  placed  the  large,  irregular-shaped 
thyroid  cartilage  which  forms  the  projection  known  as 
Adam's  apple.  The  opening  at  the  top  of  the  larynx 
is  guarded  by  a  covering  of  cartilage  fixed  to  the  top  of 
the  thyroid  ;  this  is  the  epiglottis.  Besides  these  three 
large  single  cartilages,  the  larynx  has  three  pairs  of 
smaller  ones  attached  to  the  cricoid. 


2i4  HUMAN   PHYSIOLOGY  CHAP. 

The  vocal  cords  are  stretched  across  the  opening  in 
the  larynx,  being  fastened  behind,  in  front,  and  at  the 
sides  to  some  of  the  cartilages.  The  cords  are  two  thin 
white  bands  of  elastic  tissue  formed  by  folding  the 
mucous  membrane  which  lines  the  larynx. 

Get  a  sheep's  larynx  from  your  butcher  and  notice  the  three 
large  cartilages,  the  vocal  cords,  the  lining  membrane,  and  the 
muscles  and  connective  tissue  that  hold  the  parts  in  place. 

When  air  is  inhaled  the  vocal  cords  move  apart 
because  some  of  the  muscles  of  the  larynx  contract. 
During  exhalation  they  move  slightly  together  again. 
In  producing  voice  the  vocal  cords  are  brought  close 
together  and  made  tense  by  the  action  of  small  muscles 
that  move  some  of  the  cartilages.  If  air  is  forced  out 
of  the  lungs  when  the  cords  are  in  this  position,  they  are 
made  to  vibrate  and  give  forth  a  sound. 

If  you  place  your  hand  on  the  throat  and  sing  the 
scale,  you  will  feel  the  larynx  as  a  whole  move  slightly 
up  for  the  higher  notes  and  down  for  the  lower.  For 
the  higher  tones  the  cords  are  made  more  tense  than  for 
the  lower.  The  pitch  of  the  tones  depends  upon  the  tension 
of  the  cords  and  position  of  the  larynx.  The  londness 
depends  upon  tJie  force  with  which  air  is  expelled  from 
the  lungs  or  the  distance  over  wJiich  the  cords  are  made 
to  vibrate. 

151.  Voice  Sounds. — Sounds  produced  by  the  vocal 
cords  may  differ  in  pitch  and  loudness.  But  another 
very  important  characteristic  of  the  human  voice  is  its 
sweetness  or  quality.  This  depends  chiefly  upon  the 
large  resounding  chamber  of  the  pharynx,  nose,  and 


xv  SPECIAL  USES  OF   MUSCLES  215 

mouth.  You  can  recognize  a  friend  by  his  voice  when 
you  do  not  see  him.  The  same  keys  on  the  violin, 
piano,  and  organ  do  not  sound  alike.  Just  so  no  two 
human  voices  are  alike,  even  when  pitched  precisely 
to  the  same  key.  This  individual  peculiarity  we  call 
quality  or  timbre. 

The  lips,  teeth,  tongue,  nose,  and  palate  are  used  in 
modifying  the  sounds  as  they  come  from  the  vocal 
cords,  and  are  able  to  change  them  in  a  wonderful  way. 
If  you  pinch  your  nose  so  that  no  air  can  escape 
through  it  and  then  talk,  you  will  see  what  an  important 
part  the  nasal  passages  play  in  ordinary  conversation. 
The  loss  of  a  single  tooth  is  noticed  in  a  person's 
speech.  These  organs  change  the  size  and  shape  of 
the  various  cavities  through  which  the  sound  passes  in 
speaking,  and  so  control  the  mode  of  forcing  the  breath 
out.  By  such  modifications  the  voivel  sounds  are  made 
from  the  pure  Italian  a  as  in  arm.  The  subvocals  are 
made  in  a  similar  way,  with  the  air  passages  more  ob- 
structed, as  in  the  sounds  r,  v,  m,  n,  etc.  The  aspirates 
are  mere  emissions  of  breath  more  or  less  modified  by 
the  same  organs. 

Speech  is  simply  a  proper  combination  of  sounds  to 
form  words  that  stand  for  ideas.  A  child  at  birth  has 
a  voice,  can  produce  sounds  as  in  crying  and  screaming, 
but  cannot  speak.  Language  is  acquired  by  a  very 
slow  process  of  imitation  in  which  the  child  learns  to 
control  the  muscles  involved  in  producing  the  various 
sounds.  He  must  also  learn  the  meaning  of  the  words 
used  by  others. 


216  HUMAN  PHYSIOLOGY  CHAP. 

152.  Care  of  the  Voice.  —  The  air  passages  first  need 
attention.  Enlarged  tonsils,  adenoid  growths,  and  polypi 
in  the  nose  obstruct  the  sound  waves  so  that  the  voice  is 
dull  and  unpleasant.  All  such  obstructions  should  be 
removed  as  soon  as  they  appear,  for  they  lead  not  only 
to  permanent  defects  in  the  voice  and  speech,  but  to  im- 
paired health  and  dangerous  diseases. 

Proper  singing  is  one  of  the  very  best  ways  to  culti- 
vate a  pleasant  and  strong  voice  for  speaking.  All 
children  should  be  encouraged  to  sing  simple  pieces 
within  easy  reach  of  their  voices.  Singing  is  an  excel- 
lent exercise  for  developing  a  full  chest,  expanding  the 
lungs,  and  gaining  control  of  the  muscles  of  the  larynx. 
A  child  should  not  sing  when  suffering  from  any  throat 
trouble  or  while  the  voice  is  changing,  fit  no  time  should 
one  sing  until  the  larynx  becomes  fatigued,  as  excessive 
use  of  the  voice  tends  to  weaken  the  muscles  and  may 
result  in  permanent  injury. 

Proper  breathing  exercises  under  favorable  conditions 
give  one  control  of  the  respiratory  muscles.  This  is  an 
important  matter  in  singing,  reading,  and  speaking. 
One  who  does  not  breathe  properly  can  never  have  full 
control  of  his  voice.  Exercises  in  articulation  are  valu- 
able in  giving  distinct  enunciation  and  correct  pronun- 
ciation. 

The  delicate  mucous  membrane  of  the  throat  and  the 
nose  is .  easily  irritated  and  inflamed  by  dust  of  the 
street,  smoke,  alcoholic  drinks,  hot  foods  followed  by 
ice  water,  strong  condiments,  and  exposure  to  cold. 
When  congested  and  inflamed  the  throat  feels  sore,  the 


xv  SPECIAL   USES  OF  MUSCLES  217 

muscles  and  the  vocal  cords  lose  their  power  to  respond 
to  nerve  stimuli,  and  the  voice  becomes  harsh  and  dis- 
agreeable. 

A  sweet,  pleasant,  melodious  voice  under  perfect  control 
is  a  possession  that  should  be  as  highly  prized  as  good  per- 
sonal appearance.  Much  can  be  done  to  secure  such  a 
voice  by  regular,  systematic  training  and  proper  care,  if 
begun  in  early  childhood.  A  celebrated  singer,  when 
asked  why  he  practiced  so  regularly,  said,  "  If  I  neglect 
to  practice  one  day,  I  notice  it ;  if  for  two  days,  my 
friends  notice  it;  and  if  for  three  days,  the  public  notice 
it." 

SUMMARY  OF  THE   MAIN   POINTS 

1.  The  bones  serve  as  levers  for  the  skeletal  muscles  in  all 
movements.     There  are  three  classes  of  levers,  all  of  which 
occur  in  the  body. 

2.  Standing  involves  the  use  of  a  large  number  of  muscles 
that  must  be  delicately  adjusted  in  order  to  maintain  the  body 
erect. 

3.  The    nerves   play  an  important    part   in    standing.     All 
the    muscles    must  be  stimulated   just  enough  to   maintain  a 
balance. 

4.  Walking  is  an  act  of  falling  forward  and  catching  one's 
self.     It  brings  into  play  many  of  the  large  muscles,  and  for 
that  reason  it  is  a  very  valuable  exercise. 

5.  Running  is  quite  like  walking  except   that  the  body  is 
inclined  more,  both  feet  are  never  on  the  ground  at  the  same 
time,  and  the  onward  movement  is  usually  more  rapid. 

6.  There  are  many  flat  muscles  in  the  head  and  face  which 
are  used  in  expressing  feelings  of  the  mind.     They  are  called 
muscles  of  expression. 


2i 8  HUMAN   PHYSIOLOGY  CHAP,  xv 

7.  The  vocal  cords  are  two  thin  folds  of  mucous  membrane 
stretched  across  the  open  space  in  the  larynx. 

8.  The  cords  move  apart  in  inhalation,  and  together  in  ex- 
halation.    They  may  be  stretched  tight,  and  caused  to  vibrate 
by  the  breath  as  it  is  forced  out  of  the  lungs. 

9.  Difference    in    pitch   depends  upon  differences  in  the 
tension  of  the  vocal  cords  and  in  the  position  ofthe  larynx  as 
a  whole. 

10.  Loudness  depends  upon  the  force  with  which  the  breath 
is  expelled  from  the  lungs,  and  the  distance  it  makes  the  cords 
move  in  their  vibration. 

11.  Quality  depends  upon  the  size  and  shape  of  the  pharynx, 
nasal  cavities,  and  mouth. 

12.  The  lips,  teeth,  tongue,  soft  palate,  and  nose  modify  the 
sounds  made  by  the  cords,  and  produce  the  various  tones  of 
voice. 

13.  The  air  passages  should  be  unobstructed   by  adenoid 
growths,  enlarged  tonsils,  or  polypi,  and  the  respiratory  muscles 
unhampered  by  round  shoulders,  flat  chest,  curved  spine,  or 
tight  lacing. 

14.  Voice  culture,  singing,  and  breathing  exercises  are  im- 
portant means  of  training  the  voice.     The  voice  depends  upon 
the  general  health  of  the  body. 

15.  Much  can  be  done  to  secure  a  strong,  sweet,  melodious 
voice,  and  a  pleasant,  agreeable  manner  of  speech. 

1 6.  Tobacco,  alcohol,  hot  foods  or  drinks,  cause  a  conges- 
tion and  inflammation  of  the  mucous  membrane,  and  make  the 
voice  harsh  and  disagreeable. 


CHAPTER   XVI 

THE   NERVOUS   SYSTEM 

153.  Plan  of  the  Nervous  System.  —  We  shall  now 
learn  something  about  the  system  that  regulates,  con- 
trols, and  harmonizes  the  activities  of  all  the  cells  and 
organs  of  the  body,  and  makes  us  aware  of  the  world 
about  us  and  of  our  relation  to  it. 

The  great  central  organs  of  the  nervous  system  are 
the  brain  and  the  spinal  cord.  There  are  nerves  going 
from  the  brain  to  the  millions  of  cells  in  all  parts  of  the 
body.  Nerves  come  to  the  brain  from  every  part  of 
the  body.  The  nerves  going  to  the  brain  carry  stimuli 
to  this  central  organ.  It  is  because  of  these  stimuli 
that  we  see,  hear,  taste,  smell,  feel,  and  know  what  is 
going  on  around  and  within  us.  The  brain  receives 
these  stimuli  and  sends  messages  out  over  the  nerves 
that  go  from  it,  which  tell  the  muscles,  glands,  and  other 
tissues  what  to  do  in  order  that  the  various  activities 
and  interests  of  the  body  as  a  whole  may  be  properly 
and  harmoniously  carried  on.  It  is  the  brain  that  con- 
trols the  nutrition  and  function  of  every  cell  and  makes 
it  work  at  the  right  time  and  in  the  right  way. 

The  brain  with  its  incoming  and  outgoing  nerves 
may  be  compared  to  the  central  railroad  station  with  its 

219 


FIG.  115.  —  The  nervous  system. 


CHAP.  XVI 


THE  NERVOUS  SYSTEM 


221 


numerous  telegraph  wires  running  in  all  directions,  by 

means  of  which  the  trains  moving  anywhere  on  the  line 

are    controlled.     The   train   dispatcher  /  in    the    central 

station  receives  messages  from  every  train  on  the  road, 

so  that  he  knows  just  where  every  train 

is    located    and    how  .it  is   moving.     He 

sends    messages    out  to   the   conductors, 

giving   them    their    orders    so  that  their 

trains   may  not  run  into  each  other.     A 

single  mistake  of  either  train  dispatcher 

or  conductor  in  sending  a  wrong  message 

or  in  failing  to  obey  orders,  might  result 

in  serious  loss  of  life  and  property.     One 

man   must   plan   and   operate   the   entire 

system. 

In  much  the  same  way  the  brain  per- 
forms its  duties,  which  are,  however,  very 
much  more  complicated.  If  the  muscles 
did  not  receive  orders  from  the  brain  and 
obey  them,  we  could  not  walk  or  speak, 
the  lungs  and  heart  could  not  work,  the 
foods  could  not  be  digested,  in  fact  an- 
archy would  reign  supreme  in  the  human  FIG.  n6.  —  The 

brain  and  spi- 

body.     We  shall  now  study  this  wonder-        nal  cord  from 
ful  system  in  detail.  behind  (Pratt)- 

154.  Nerve  Tissue.  —  The  nerve  tissue  consists  of 
cells  which  in  size  and  shape  are  very  unlike  those 
found  in  any  other  tissue.  They  have  a  cell  body  and 
a  large  nucleus,  made  up  of  a  very  soft,  delicate  sub- 
stance. Each  nerve  cell  sends  out  a  principal  projec- 


HUMAN   PHYSIOLOGY 


CHAP. 


FIG.  117. —  Nerve  cells  of  a  rat 
(Pratt) , 


tion    called   the    axone,    and    several    shorter,    treelike 

branches  called  dendrites.     Every  nerve  cell  has  a  cell 

body,  an  axone,  and  den- 
drites. Some  nerve  cells  with 
their  projections  are  very 
long.  A  cell  body  located  in 
the  spinal  cord  of  the  neck, 
sends  its  axone  out  to  the  fin- 
gers, and  some  in  the  lower 
part  of  the  cord  send  their 
axones  to  the  toes.  A  single 

nerve  fiber  may  extend  the  whole  length  of  the  arm  or 

of  the  leg.    Some  of  the  cell 

bodies  of  the  cord  are  large 

enough  to  be  seen  with  the 

naked  eye.    Others  are  very 

small  and  have  short  axones 

and  dendrites. 

The    dendrites    serve    to 

connect  one  cell  with  other 

cells  and  carry  messages  to 

the  cell  bodies  of  which  they 

form  a  part.     The  cell  body 

receives   the    message    over 

the  dendrites  and  directs  it 

out    over    its    axone.      The 

axone   carries    the  message 

from  the  cell  body  to  a  muscle  or  to  a  gland.     Some- 
times the  dendrites  are  very  long,  bringing  messages  a 

long  distance. 


FlG.  118.  —  Human  nerve  cell,  show- 
ing dendrites,  cell  body,  and 
axone.  (From  Huxley.) 


xvi  THE  NERVOUS   SYSTEM  223 

All  nerve  tissue  consists  of  such  cells  completely  sur- 
rounded and  held  together  by  connective  tissue  and  fat. 
These  substances  protect,  pack  in,  and  hold  in  place  the 
delicate  nerve  tissue  and  enable  it  to  carry  on  its  func- 
tions properly  and  easily.  The  entire  nervous  system  is 
made  up  of  nerve  cells  and  connective  tissue. 

Take  a  bit  of  nerve  tissue  and  examine  it  under  the  microscope. 
Notice  the  size  and  shape  of  nerve  cells. 

155.  The  Nerves. — We  saw  that  there  are  two  kinds 
of  nerves  necessary,  one  leading  to  and  the  other  from 
the  brain.  The  former  are  called  sensory  or  afferent, 
and  the  latter  motor  or  efferent.  Many  of  the  nerves 
do  not  go  directly  to  the  brain,  but  reach  it  through  the 
spinal  cord,  and  for  that  reason  are  known  as  spinal 
nerves.  There  are  tJiirty-one  pairs  of  this  kind.  They 
carry  stimuli  from  and  send  impulses  to  the  muscles 
and  glands  of  the  trunk  and  the  extremities.  Those 
connected  directly  with  the  brain  are  called  cranial 
nerves.  TJiere  are  twelve  pairs  of  cranial  nerves.  The 
cranial  nerves  are  distributed  to  the  head  and  to  the 
internal  organs.  All  of  the  special  senses  except  touch 
or  feeling  have  this  class  of  nerves  coming  from  them. 
The  olfactory  of  the  nose,  the  optic  of  the  eye,  and  the 
auditory  of  the  ear  are  examples  of  cranial  nerves. 

In  their  appearance  all  nerves  are  quite  alike.  They 
are  smooth,  white,  shining  cords  of  various  sizes  and 
lengths.  The  great  sciatic  nerve  of  each  lower  limb  is 
about  one  half  of  an  inch  wide,  one  sixth  of  an  inch  in 
thickness,  and  extends  from  the  lower  end  of  the  spinal 
cord  down  to  the  toes,  sending  off  branches  all  along  its 


224 


HUMAN   PHYSIOLOGY 


CHAP. 


course.  Some  nerves  are  very  short 
and  so  small  that  they  can  scarcely 
be  seen  with  the  naked  eye. 

If  a  nerve  is  cut  across  and  exam- 
ined under  the  microscope,  it  will 
be  seen  to  consist  of  many  very 
fine  nerve  threads  or  fibers,  held  to- 


FlG.  119. — A  section  of  a  frog's  nerve,  showing 
the  sheath  and  nerve  fibers. 

gether  by  fatty  connective  tissue  and 
the  whole  surrounded  by  a  sheath. 
Each  fiber  is  an  outgrowth  of  a 
nerve  cell,  an  axone  or  a  dendrite, 
and  runs  to  its  destination  unbroken 
like  a  single  continuous  wire  of  a 
large  cable.  A  large  nerve  has 
thousands  of  separate  fibers. 


I 


-Node 


FIG.  120.  —  Showing  A,  a  nerve  cell  with  all  its  parts  —  dendrites,  cell  body,  and 
axone;  and  B,  a  portion  of  a  nerve  fiber,  highly  magnified.   (Drawn  by  Pratt.) 


xvi  THE  NERVOUS  SYSTEM  225 

A  nerve  fiber  differs  from  a  telegraph  or  telephone 
wire  in  that  it  carries  messages  in  one  direction  only, 
while  a  wire  will  carry  messages  in  either  direction. 
A  sensory  fiber  conveys  messages  to  the  brain  or  spinal 
cord,  but  never  from  it ;  while  a  motor  fiber  carries 
messages  out  to  muscles  and  glands,  but  it  cannot 
carry  impressions  to  the  brain.  All  of  the  spinal  nerves 
and  three  pairs  of  cranial  nerves  contain  both  sen- 
sory and  motor  fibers  and  therefore  are  called  mixed 
nerves. 

156.  The  Spinal  Cord. — The  spinal  cord  is  a  great 
nerve  trunk  extending  from  the  base  of  the  skull  down 
through  the  canal  of  the  vertebrae  or  backbone.  In  the 
adult  it  is  about  eighteen  inches  long  and  three  quarters 
of  an  inch  in  diameter.  The  spinal  cord  and  brain  are 
carefully  protected  by  a  bony  covering,  but  besides  this 
there  are  three  membranes 
that  closely  invest  these  deli-  V 
cate  organs  and  supply  them 
with  nutrition. 

The  outer  part  of  the  spi- 
nal cord  is  called  ivhite  matter.          ^r^*-  "war 
It  consists  of  bundles  of  nerve           ^^^^J  \~~~*^^   * 
fibers  that  serve  as  ingoing     FIQ    I2I._showing  the  white 

and   OUtCOming   pathways   for  and  gray  matter  of  the  spinal 

the  sensory  and  motor  mes-         cord  (Pratt), 
sages   carried    to   and    from   the  brain.      White  matter 
always  means  nerve  fibers  and  never  does  anything  except 
carry  messages.     The  entire  surface  of  the  body  except 
the  head  and  face  is  supplied  with  spinal  nerves. 

Q 


226  HUMAN  PHYSIOLOGY  CHAP. 

The  central  portion  of  the  spinal  cord  consists  of 
nerve  cell  bodies  and  is  known  as  gray  matter.  In  the 
cord  we  find  the  white  matter  on  the  outside  and  the 
gray  on  the  inside.  The  nerve  cells  or  gray  matter  do 
not  carry  messages ;  they  have  very  different  functions 
to  perform.  A  collection  of  nerve  cells  that  has  some 
particular  work  to  do  is  called  a  nerve  center.  The 
cells  of  the  gray  matter  of  the  spinal  cord  are  grouped 
into  a  great  many  nerve  centers  which  perform  important 
offices.  These  centers  control  most  of  our  involuntary 
movements,  and  do  a  large  amount  of  work  that  can  be 


rp/na/mrve 


FlG.  122. — A  cross-section  of  the  spinal  cord,  showing  a  spinal  nerve  and  its 
two  roots  (Huxley). 

done  without  the  aid  of  the  brain.  Certain  sensory 
impressions  carried  to  the  cord  do  not  reach  the  brain 
at  all,  but  are  reflected  or  turned  back  to  muscles  by 
such  centers  located  in  the  cord  ;  they  act  independently 
of  the  brain.  These  are  reflex  acts. 

Get  a  piece  of  spinal  cord  from  the  meat  market  and  examine  it 
when  fresh.  It  may  then  be  hardened  by  using  a  mixture  of  two 
thirds  alcohol  and  one  third  2  per  cent  solution  of  formalin.  When 
it  is  thus  preserved,  slices  may  be  easily  cut  for  more  careful  study 
with  a  magnifying  glass. 

Centers  of  the  cord  control  the  nutrition  and  growth 
of  the  cells  of  the  body  by  telling  them  when  and  how 
much  to  eat,  and  by  regulating  their  blood  supply. 


XVI 


THE  NERVOUS   SYSTEM 


227 


The  digestion  of  foods,  the  action  of  the  liver,  the  dis- 
tribution of  blood,  and  many  other  important  functions 
are  under  the  control  of  these  reflex  centers.  No 
thought  need  ever  be  given  to  the  work  of  the  spinal 
cord,  and  so  the  brain  is  left  free  to  do  other  things. 


Cerebrum 


FIG.  123.  — The  left  half  of  the  brain,  inner  surface  (Hebert). 

157.  The  Brain.  —  The  brain  is  the  organ  of  the  mind 
and  the  seat  of  consciousness.  It  enables  us  to  see, 
hear,  taste,  smell,  and  feel ;  to  remember,  imagine,  and 
think ;  to  love  and  hate ;  to  will  and  execute.  It  is  the 
organ  of  the  human  soul. 


228  HUMAN   PHYSIOLOGY  CHAP,  xvi 

The  brain  occupies  the  entire  cavity  of  the  cranium 
and  consists  of  four  parts  or  divisions,  called  the  bulb, 
pons,  cerebellum,  and  cerebrum.  The  cerebrum  forms 
about  four  fifths  of  the  whole  mass  and  is  by  far  the  most 
important  part  of  the  nervous  system.  The  elephant's 
brain  weighs  from  nine  to  ten  pounds,  the  whale's 
about  five  pounds,  and  man's  a  little  over  three  pounds. 
The  intelligence  of  an  animal  does  not  depend  upon  the 
actual  weight  of  the  brain.  While  the  average  brain 
weight  in  man  is  about  three  pounds,  quite  wide  varia- 
tions from  this  have  been  found.  The  brain  of  Cuvier, 
the  French  naturalist,  weighed  sixty-six  ounces ;  that  of 
Byron,  the  poet,  sixty-four  ounces  ;  that  of  Schiller,  fifty- 
six  ounces  ;  that  of  Gauss,  the  mathematician,  fifty-three 
ounces  ;  and  that  of  Dante  fifty  ounces.  The  brains 
of  some  idiots  have  outweighed  these,  while  those  of 
some  of  the  most  intelligent  men  have  fallen  below  the 
average.  We  cannot  maintain  that  there  is  always  a 
very  close  relation  between  a  man's  intelligence  and 
the  size  of  his  head. 

The  order  of  intelligence  depends  more  upon  the 
number  and  size  of  the  nerve  cells  that  occur  in 
the  surface  layer  of  the  brain,  and  therefore  upon 
the  number  and  depth  of  the  convolutions  or  wrinkles 
which  go  to  increase  the  surface  area.  The  gray  mat- 
ter is  on  the  surface  in  the  brain  and  the  white  matter  on 
the  inside.  The  brain  of  the  higher  animals  and  of  man 
is  not  smooth  on  the  surface,  as  can  be  seen  from  the 
figures  opposite.  In  civilized,  highly  educated,  and 
intelligent  people  these  convolutions  are  numerous  and 


Fish. 


Reptile. 


Marsupial. 


Ap-. 


Man. 


FIG.  124.  —  A  series  of  brains,  showing  the  development  from  the  lower  to  the 
higher  animals.     (Adapted  from  various  sources  by  Pratt.) 


230 


HUMAN   PHYSIOLOGY 


CHAP. 


deep,  and  so  increase  the  amount  of 
gray  matter  on  the  surface  without  any 
material  increase  in  the  brain  weight. 

1.  Get  a  sheep's  brain  from  your  butcher  and 
find  the  cerebrum,  cerebellum,  pons,  and  bulb. 

2.  Locate  the  frontal,  parietal,  temporal,  and 
occipital  lobes  of  the  cerebrum. 

3.  Notice  the  fissures  and  convolutions  in  the 
different  lobes. 

4.  Observe    how    the    two    hemispheres    are 
joined  together. 

158.  The  Bulb.  —  The  bulb  or  medulla 
is  a  slight  enlargement  at  the  upper  end 
of  the  spinal  cord.  •  It  looks  very  much 
like  the  cord,  but  it  has  a  rougher  sur- 
face. The  white  matter  of  the  cord 
continues  up  through  the  bulb  and  leads 
to  cell  bodies  on  the  surface  of  the  cere- 
brum. In  tJie  bulb  most  of  the  nerve"' 
fibers  cross  to  tJic  otJier  side  before  they 
go  in  or  out.  This  explains  how  the  left 
side  of  the  brain  controls  the  right  half 
of  the  body,  and  the  right  brain  the  left  half.  When 
the  left  brain  is  paralyzed,  the  organs  on  the  right  side 
of  the  body  are  affected ;  the  right  arm  and  the  right 
leg  do  not  work  as  they  should,  for  the  nerves  do  not 
stimulate  them. 

There  are  nerve  centers  in  the  bulb  that  control  many 
of  the  higher  reflex  muscular  activities,  as  breathing, 
masticating,  sucking  and  swallowing,  sneezing,  hic- 
coughing, the  secretion  of  digestive  fluids  and  sweat,  the 


FIG.  125.  —  The  ner- 
vous system  of  a 
pigeon.  (Drawn 
by  Pratt.) 


xvi  THE  NERVOUS   SYSTEM  231 

heart  beat,  the  tone  of  muscles,  the  size  of  blood  vessels, 
etc.  Because  so  many  important  centers  are  located  in 
the  bulb,  it  has  been  called  the  vital  knot. 

The  pom  lies  just  in  front  of  the  bulb  and  serves 
chiefly  as  a  bridge  to  connect  the  cerebrum  with  the 
other  parts  of  the  brain. 

159.  The  Cerebellum.  — The  cerebellum  or  little  brain 
has  the  gray  matter  on  the  outside  and  the  white  within. 
The  white  matter  radiates  from  the  center  to  all  parts 
of  the  surface,  giving  it  a  treelike  appearance  when  cut 
open,  and  for  this  reason  it  is  called  the  tree  of  life.     It 
forms  about  one  eighth  of  the  entire  brain,  and  consists 
of  two  closely  connected  halves,  each  furrowed  by  nu- 
merous shallow  convolutions. 

The  uses  of  the  cerebellum  are  not  fully  known  at 
present,  but  we  know  that  it  has  to  do  with  balancing 
the  body  in  standing,  walking,  and  running,  and  in  mak- 
ing the  muscles  work  together  in  these  movements. 
When  the  cerebellum  of  any  animal  is  diseased,  injured, 
or  removed,  it  is  unable  to  guide  and  control  its  muscles 
of  locomotion. 

160.  The  Cerebrum.  —  The  cerebrum  is  nearly  divided 
into  two   hemispheres  by  a  deep  longitudinal  cleft  or 
fissure.     Each  hemisphere  is  marked  by  several  deep 
fissures  and  many  small  ones,  which  divide  it  into  four 
main  parts  called  lobes,  each  having  numerous  convolu- 
tions.    These  lobes  are  known  as  the  frontal,  parietal, 
temporal,  and  occipital.     See  figures  123  and  126.     The 
gray  matter,  which  varies  in  thickness  from  one  twelftJi 
to  one  sixth  of  an  inch,  forms  the  entire  outer  surface 


232 


HUMAN   PHYSIOLOGY 


CHAP. 


Cerebrum 


of  the  cerebrum.  It  extends  down  into  every  fissure 
and  up  over  every  convolution,  and  in  this  way  the  area 
of  the  gray  matter  is  increased  many  fold. 

The  cells  of  the  cerebrum  are  also  grouped  into  defi- 
nite centers,  each  having  its  own  work  to  do  and  never 
attempting  anything  else.  The  centers  may  be  said 

to  belong  to  one  of  three 
kinds ;  namely,  sensory, 
motor,  or  association.  The 
sensory  areas  are  those 
parts  of  the  cerebrum  to 
which  impressions  are  car- 
ried by  the  sensory  nerves. 
We  notice  in  the  diagram 
that  a  part  of  the  occipital 
lobe  is  the  center  for  sight, 
the  temporal  for  taste, 
smell,  and  hearing,  and  the 
upper  and  inner  part  of 
the  parietal  for  touch.  The 
motor  areas  have  to  do 
with  sending  messages  out  over  efferent  nerves  to  the 
different  voluntary  muscles  of  the  body.  We  see  in 
the  diagram  that  the  parietal  and  a  small  part  of  the 
frontal  lobes  constitute  the  motor  area.  If  any  cells  of 
the  motor  area  are  stimulated  with  electricity,  a  definite 
muscular  response  will  always  follow.  By  such  experi- 
ments the  use  of  every  part  of  the  motor  area  has  been 
fully  mapped  out.  The  association  areas  are  neither 
motor  nor  sensory,  but  are  very  highly  developed  in  man, 


FIG.  126.  —  Showing  the  lobes  of  the 
brain  and  their  functions  (Zuppke). 


XVI 


THE  NERVOUS   SYSTEM 


233 


FlG.  127.  —  Outer  surface  of  the  right  hemisphere. 
The  dots  indicate  the  sensory,  the  lines  the 
motor,  and  the  clear  spaces  the  association 
areas.  (Modified  from  Flechsig  by  Pratt.) 


and  doubtless  have  some  important  function.     It  is  now 

believed  by  some  scientists  that   the  three  association 

areas  are  thought 

centers.     The  sen- 
sory   impressions, 

it  is  claimed,  are 

carried    from   the 

sensory   areas    to 

the   association 

areas,    and    from 

them  to  the  motor 

area  by  means  of 

nerve  fibers  which 

connect     these 

parts  with  each  other.     These  association  areas  may  be 

the  centers   for   memory,  imagination,   and   judgment. 

All  this,  however, 
is  largely  theoreti- 
cal at  present. 

The  brain  has 
three  kinds  of 
nerve  fibers.  First, 
those  that  carry 
impressions  up 
from  the  spinal 
cord  to  the  sensory 
areas,  and  down 
from  the  motor 

areas ;   they  are  called  projection  fibers.     Second,  those 

that  connect  different  parts  of  the  two  hemispheres  with 


FlG.  128.  —  Inner  surface  of  the  left  hemisphere. 
The  dots  indicate  the  sensory,  the  lines  the 
motor,  and  the  clear  spaces  the  association 
areas.  (Modified  from  Flechsig  by  Pratt.) 


234 


HUMAN   PHYSIOLOGY 


CHAP. 


each  other ;  they  are  called  commissural  fibers.     Third, 
those  that  connect  the  lobes  and  convolutions  in  each 


FIG.  129.  —  Projection  fibers 
(Zuppke) . 


FIG.  130.  —  Commissural  fibers 
(Zuppke). 


hemisphere  ;  they  are  known  as  association  fibers.     By 
means  of  the  different  kinds  of  nerve  fibers  every  part 

of  the  body,  fingers  and 
toes,  elbows  and  knees, 
shoulders  and  hips,  eyes 
and  ears,  is  connected  with 
the  cerebrum  and  may 
send  information  to  it,  and 


FIG.  131.  —  Association  fibers 
(Zuppke). 


receive  responses  and  mes- 
sages from  it. 

161.  The  Sympathetic  Nervous  System.  —  We  have 
learned  that  there  are  twelve  pairs  of  cranial  nerves 
which  branch  off  from  the  brain,  and  pass  out  of  the 
skull  through  openings  in  the  bones  and  distribute 
themselves  to  many  organs  of  the  head,  chest,  and 
abdomen ;  and  thirty-one  pairs  of  spinal  nerves  which 
connect  the  cord  with  the  skin,  and  with  all  the  skeletal 
muscles  except  some  about  the  head  and  face.  Besides 


xvi  THE  NERVOUS   SYSTEM  235 

these  there  is  another  group  of  nerves  and  nerve  centers 
known  as  the  sympathetic  system.  It  consists  of  a  chain 
of  ganglia — forty-nine  in  all — located  on  either  side  of 
the  spinal  cord,  extending  from  the  base  of  the  brain  to 
the  coccyx.  It  has  also  four  great  ganglia,  situated 
a  little  in  front  of  the  chain,  together  with  numerous 
smaller  ganglia  located  in  the  visceral  organs.  Many 
nerves  connect  all  these  ganglia  with  each  other,  with 
the  spinal  cord  and  brain,  and  with  the  organs  of  the 
chest  and  abdomen.  The  largest  of  the  four  ganglia  is 
called  the  solar  plexus.  It  is  located  behind  the  stomach 
and  in  front  of  the  aorta,  and  sends  branches  to  all  the 
organs  of  the  abdomen,  as  the  stomach,  liver,  spleen, 
pancreas,  kidneys,  and  intestines.  These  ganglia  all 
give  off  nerves  that  supply  the  visceral  organs,  glands, 
and  the  walls  of  the  arteries  and  capillaries. 

These  ganglia  and  nerves  help  to  regulate  the  size  of 
the  blood  vessels,  control  the  action  of  the  involuntary 
muscles  of  all  the  visceral  organs,  as  lungs,  heart, 
stomach,  and  intestines,  and  regulate  the  activity  of  the 
secreting  glands.  They  seem  to  exercise  an  important 
control  over  the  vital  processes  that  are  carried  on 
unconsciously. 

Most  of  the  internal  organs  have  nerves  from  the 
sympathetic  system  and  from  the  cerebro-spinal  system, 
as  the  other  is  called.  The  two  systems  form  one  com- 
plete, unified  nervous  apparatus. 

162.  Mind  and  Brain.  —  We  know  that  the  mind  and 
the  brain  are  very  closely  connected,  but  just  what 
their  relation  to  each  other  is  no  one  can  tell.  When 


236  HUMAN   PHYSIOLOGY  CHAP. 

the  mind  is  active  more  blood  goes  to  the  brain,  oxida- 
tion is  increased,  the  temperature  rises,  and  the  brain 
cells  become  fatigued.  When  the  brain  is  seriously 
injured  or  diseased,  the  mind  does  not  work  as  it 
should ;  the  person  behaves  in  a  strange  way.  He  can- 
not remember,  imagine,  and  reason  as  he  once  could  ; 
his  feeling  and  will  power  are  lost  or  enfeebled ;  his 
whole  mind,  with  all  its  powers  and  capacities,  hopes 
and  ambitions,  has  become  so  deranged  that  he  cannot 
be  held  responsible  for  what  he  does,  and  we  call  him 
mad  or  insane. 

Sometimes  a  person  suddenly  loses  the  ability  to 
speak.  A  judge  of  the  Supreme  Court  in  one  of  our 
states,  after  spending  an  evening  in  pleasant  conversa- 
tion with  some  friends  at  his  house,  retired  at  his  usual 
time,  apparently  in  the  best  of  health.  The  next  morn- 
ing he  could  not  utter  a  single  sentence.  The  power 
of  speech  was  gone.  He  was  as  helpless  as  if  he  had 
never  learned  to  talk.  After  a  vacation  of  several 
months  he  recovered  fully.  Cases  of  this  kind  are 
known  to  physicians,  for  they  are  not  uncommon.  The 
loss  of  speech  is  sometimes  due  to  the  formation  of  a 
blood  clot  over  the  speech  area  of  the  brain  caused  by 
the  rupture  of  small  blood  vessels.  In  such  cases  the 
skull  has  been  opened  and  the  hard  clot  carefully  re- 
moved without  injuring  the  delicate  brain  tissue,  and 
the  ability  to  speak  was  regained  in  the  course  of  a  few 
weeks.  When  no  operation  is  performed,  the  clot  may 
in  time  be  completely  absorbed  so  that  the  patient  re- 
covers. 


xvi  THE  NERVOUS   SYSTEM  237 

While  we  do  not  know  just  how  the  mind  and  the 
brain  are  related,  we  do  know  that  a  strong,  sound,  and 
vigorous  mind  demands  a  trained,  healthy,  and  well- 
nourished  brain  and  body. 

SUMMARY   OF  THE   MAIN   POINTS 

1.  The  nervous  system  controls,  regulates,  and  brings  into 
harmonious  relation  all  the  cells,  tissues,  organs,  and  systems 
of  the  human  body. 

2.  The  nervous  system  consists  of  nerves  and  nerve  centers. 
There  are  nerves  from  every  cell  in  the  body  going   to    the 
brain,  and  from  the  brain  to  all  the  muscles  and  glands. 

3.  A  nerve  cell  consists  of  a  cell  body  with  a  large  nucleus, 
a  main  projection,  the  axone,  and  a  number  of  treelike  pro- 
longations  called   dendrites.     They   vary  much   in   size  and 
shape. 

4.  The  dendrites  carry  messages  to  the  cell  body,  and  the 
axone  away  from  the  cell  body. 

5.  A  nerve  consists  of  a  large  number  of  nerve  fibers  bound 
together  with  connective   tissue   and  fat  into  a  single  trunk. 
Each  fiber  is  either  an  axone  or  a  dendrite  of  some  nerve  cell. 

6.  As  to  origin,  we  divide  nerves  into  spinal  and  cranial,  and 
as  to  function,  into  sensory,  motor,  and  mixed. 

7.  The  white  matter  of  the  cord  forms  pathways  for  the 
ingoing  impressions  and  the  outgoing  impulses,  and  the  gray 
matter,  the  central  portion,  consists  of  nerve  centers  for  many 
of  the  lower  reflex  acts. 

8.  The  brain  is  the  central  organ  of  the  nervous  system,  and 
consists  of  the  bulb,  the  pons,  the  cerebellum,  and  the  cere- 
brum.    It  weighs  about  fifty  ounces  in  man,  and  has  a  very 
rough  or  furrowed  surface. 

9.  In  the  bulb  at  the  upper  end  of  the  spinal  cord,  most  of 
the  nerve  fibers  cross  to  the  opposite  side.     The  gray  matter 


238  HUMAN   PHYSIOLOGY  CHAP,  xvi 

is  grouped  into  nerve  centers,  which  control  many  of  the  higher 
vital  functions,  as  breathing,  heart  beat,  swallowing,  secretion, 
etc. 

10.  The  pons,  or  bridge,  is  a  mass  of  nerve  fibers  connect- 
ing the  bulb,  cerebellum,  and  cerebrum. 

1 1.  The  cerebellum,  or  little  brain,  is  the  organ  which  makes 
the  muscles  used  in  sitting,  standing,  walking,  and  balancing 
work  together  in  the  right  order,  and  gives  us  our  bearings  in 
space. 

12.  The  cerebrum  is  the  largest  part  of  the  brain,  forming 
about  four  fifths  of  the  entire  mass.     It  consists  of  two  hemi- 
spheres, each  having  four  main  lobes,  known  as  the  frontal, 
parietal,  temporal,  and  occipital. 

13.  There    are   numerous  nerve   centers  in   the  cerebrum, 
each  having  its  special  function  to  perform.     The  three  im- 
portant areas  are  known  as  the  sensory,  the  motor,  and  the 
association. 

14.  The  sensory  areas  receive  impressions  from  the  sensory 
nerves  coming  from  all  parts  of  the  body.     The  motor  areas 
send  out  messages  over  the  motor  nerves  to  the  muscles  and 
glands.      The   association  areas  connect  the  sensory  and  the 
motor   areas  of  the   brain,  and   may  serve  as  the  centers  for 
thought. 

15.  The  ganglia  and  nerves  of  the  sympathetic  system  supply 
all  the  organs  of  the  chest  and  abdomen.     These  organs  are 
also  supplied  with  spinal  and  cranial  nerves,  so  that  they  have  a 
double  nerve  supply. 

1 6.  The  brain  and  the  mind  stand  in  close  relation  to  each 
other.     If  we  wish  a  strong,  active,  vigorous  mind,  we  must  see 
that  the  brain  is  kept  in  an  excellent  physical  condition. 


CHAPTER   XVII 

CARE  AND  TRAINING  OF  THE  NERVOUS  SYSTEM 

163.  Food  and  Air.  —  The  spinal  cord  and  the  brain 
are  sometimes  called  the  master  organs,  because  the 
growth  and  activity  of  every  cell  in  the  body  are  under 
their  direct  control.  Glands  and  muscles  act  only 
when  stimulated  by  nerves.  Hence  the  nervous  system 
is  carefully  protected  against  injury,  and  has  a  large 
proportion  of  the  blood  carried  to  it.  The  brain  is 
about  one  forty-fifth  of  the  weight  of  the  entire  body, 
but  it  receives  about  one  eighth  of  the  whole  quantity  of 
blood. 

It  requires  a  large  amount  of  food  to  keep  the  deli- 
cate brain  cells  in  a  good  working  condition.  The 
health  of  the  brain  and  the  kind  and  amount  of  work  it 
can  do  depend  upon  the  quantity  and  quality  of  the 
blood  sent  to  it.  The  boy  or  girl  who  eats  only  coffee 
and  rolls  for  breakfast,  and  attempts  to  do  hard  school 
work  all  forenoon  on  that  scanty  and  unhygienic  meal, 
must  not  be  surprised  if  he  becomes  exhausted  and 
suffers  from  headache  in  the  latter  part  of  the  morning 
exercise.  A  schoolboy  needs  a  good  supply  of  nutri- 
tious and  easily  digested  food  three  times  a  day,  and  a 
light  lunch  in  the  middle  of  the  forenoon,  if  he  wishes 
to  do  the  best  kind  of  mental  work. 

239 


240  HUMAN   PHYSIOLOGY  CHAP. 

The  amount  and  kind  of  air  breathed  is  next  in  im- 
portance to  the  food  eaten.  Since  the  brain  needs  so 
much  food,  it  must  have  an  equally  abundant  supply  of 
pure  fresh  air  to  oxidize  the  food.  The  "  school  head- 
aches "  are  the  result  of  hot,  close,  poorly  ventilated 
schoolrooms,  in  which  the  same  air  must  be  breathed 
over  and  over  again,  until  the  pupils  become  so  drowsy 
and  listless  that  they  cannot  get  their  lessons.  Such  a 
condition  is  sure  to  cause  severe  headaches  and  other 
disorders. 

164.  Exercise.  —  The  brain,  like  the  muscles,  must  be 
given  a  moderate  amount  of  exercise  daily  to  keep  it 
well  and  strong.  It  becomes  delicate,  weak,  and  sickly 
if  not  used,  just  like  the  muscles  of  an  arm  carried  in  a 
sling.  Studying  may  at  first  be  hard  work,  and  very 
fatiguing,  but  if  kept  up  day  after  day,  with  proper 
intervals  of  rest,  it  will  soon  become  easy,  so  that  diffi- 
cult tasks  are  a  real  pleasure. 

In  studying  exercise,  we  learned  that,  in  order  to  use 
all  the  muscles  of  the  body,  a  great  variety  of  move- 
ments is  essential.  In  the  same  way  a  single  power  of 
the  mind  can  be  exercised  and  all  the  others  neglected. 
Variety  in  mental  work  is  just  as  important  as  in  physi- 
cal work  to  call  into  activity  all  the  capacities  and  powers 
of  the  human  mind.  The  cerebrum  alone  contains,  on 
its  outer  surface,  over  9,200,000,000  cells  which  can  be 
used.  In  order  to  bring  all  these  cells  into  action,  so 
that  they  may  grow  and  develop  as  they  should,  a  very 
great  variety  of  mental  exercise  and  a  wide  range  of 
interests  are  indispensable. 


xvii      CARE  AND  TRAINING  OF  THE  NERVOUS  SYSTEM      241 

165.  Education.  —  Education  means  the  proper  exer- 
cise of  all  the  parts  of  the  brain  so  as  to  bring  about  a 
symmetrical  development  of  the  various  brain  centers. 
One  of  the  chief  reasons  why  we  study  so  many  differ- 
ent branches  in  the  schools  is  to  exercise  and  develop 
the  whole  brain.  This  trains  the  intellect,  the  emotions, 
and  the  will,  and  develops  character. 

In  early  life  all  the  senses  should  be  properly  and 
adequately  exercised,  and  the  larger  muscles  brought 
under  the  control  of  the  will.  The  exercises  of  the 
kindergarten  and  the  primary  school  are  designed  to 
train  and  develop  the  sensory  areas  of  the  brain,  and  to 
bring  into  relation  with  them  the  motor  centers  of  the 
hands  and  feet.  Nature  herself  has  surrounded  us 
with  things  beautiful  and  interesting,  as  the  birds  and 
butterflies,  the  flowers  and  trees,  the  rocks  and  streams, 
the  clouds  and  stars,  which  are  among  the  most  valua- 
ble means  of  training  the  senses  through  close  and 
accurate  observation.  Literature  is  full  of  references 
to  objects  in  nature,  and  so  may  be  useful  in  training 
the  imagination  if  the  reader  will  take  the  time  to  recall 
and  picture  each  object  mentioned.  Manual  training 
is  the  best  possible  means  of  exercising  the  motor  areas 
of  the  brain. 

Youth  is  the  time  when  strong  and  lasting  interests 
should  be  cultivated  in  the  many  things  concerning 
man  and  nature  about  us ;  for  as  we  grow  older  our 
interests  must  become  more  and  more  limited  in  their 
range  until  they  are  confined  to  our  business  or  pro- 
fession. The  business  man  usually  has  little  time  or 


242  HUMAN   PHYSIOLOGY  CHAP. 

energy  to  devote  to  things  not  related  to  his  own  work, 
and  therefore  all  his  interests  are  likely  to  become 
centered  in  his  own  business.  The  same  is  true  of  the 
professional  man.  Unless  a  person  gets  a  broad  and 
liberal  education,  which  trains  and  develops  the  whole 
brain,  in  youth  and  early  manhood,  he  will  not  have  a 
wide  range  of  sympathies  and  interests  in  later  life. 
Herein  lies  much  of  the  value  of  a  high  school  and 
college  education. 

166.  Habit.  —  If  a  piece  of  paper  is  folded  once,  it 
will  be  impossible  to  remove  the  crease,  and  the  paper 
will  tend  to  fold  in  the  same  way  again.  The  coat  or 
dress  sleeve  will  soon  become  wrinkled  so  that  it  is 
impossible  to  press  the  wrinkles  out ;  they  all  reappear 
when  the  garment  is  put  on.  No  one  can  wear  your 
old  shoes,  for  they  have  become  fitted  to  your  feet  and 
cannot  fit  anybody  else.  If  a  young  gourd  be  put  into 
a  bottle  and  allowed  to  grow,  it  will  take  on  the  shape 
of  the  bottle,  whatever  that  may  be,  and  will  always 
retain  that  form.  A  young  growing  tree  may  be  bent 
in  any  way,  and  in  time  it  assumes  that  shape.  "  As 
the  twig  is  bent  so  the  tree  is  inclined." 

These  examples  illustrate  an  important  principle  that 
shows  itself  on  every  hand,  and  is  known  as  the  law  of 
habit.  This  law  applies  to  animal  life  as  well,  and  man 
is  no  exception.  There  are  two  principles  of  this  great 
law  to  be  remembered.  First,  habits  are  most  easily 
formed  in  early  life,  as  in  the  young  plant,  and  in 
childhood  and  youth.  At  this  time  the  tissues  are  most 
easily  bent  and  fashioned  because  they  are  still  plastic. 


xvn       CARE  AND  TRAINING  OF  THE  NERVOUS  SYSTEM      243 

Second,  habits  are  most  easily  formed  during  periods 
of  most  rapid  growth  and  of  greatest  nutrition.  The 
young  tree  can  be  best  bent  during  the  spring  and 
early  summer,  when  the  sap  flows  freely.  Physical 
habits  can 'be  acquired  most  easily  during  the  years  of 
rapid  physical  growth.  Mental  habits  are  most  readily 
formed  when  the  brain  grows  fastest,  because  every 
mental  habit  is  due  to  a  change  of  some  sort  in  the 
brain  structure.  While  the  brain  is  plastic,  the  nutri- 
tion good,  and  the  growth  rapid,  habits  are  formed 
which  permanently  change  the  structure  of  the  brain 
cells.  Habits  are  formed  for  life  because  we  cannot  get 
rid  of  our  brains.  We  can  now  understand  why  it  is  so 
difficult  to  break  a  habit. 

The  formation  of  habits  begins  in  early  infancy.  The 
nurse  feeds  the  infant  at  regular  intervals  of  about  two 
hours,  and  it  always  gets  hungry  on  time.  If  the  infant 
is  put  to  sleep  at  ten  o'clock,  it  soon  gets  sleepy  at  that 
time  every  day.  So  we  have  habits  of  sleeping,  eating, 
working,  walking,  standing,  breathing,  thinking,  feel- 
ing, and  willing.  Some  one  has  aptly  said,  "  Man  is  a 
walking  bundle  of  habits."  All  our  personal  or  physi- 
cal habits  are  fixed  for  life  before  the  age  of  twenty  is 
reached,  and  our  business  or  professional  habits  before 
thirty. 

By  forming  good,  useful  habits,  the  entire  nervous 
system  becomes  our  most  powerful  ally,  the  brain  be- 
comes our  strong  friend ;  but  if  bad,  slovenly  habits  are 
formed,  the  nervous  structure  becomes  a  hostile  foe  and 
a  dangerous  enemy.  Habit  simplifies  all  of  our  move- 


244 


HUMAN   PHYSIOLOGY 


CHAP. 


ments  and  makes  them  more  accurate.  It  makes  many 
matters  of  daily  routine,  as  dressing  and  undressing, 
entirely  mechanical,  and  leaves  the  mind  free  to  do 
other  things. 

167.  Fatigue  and  Overwork.  —  Whenever  brain  cells 
work  they  consume  foods,  produce  wastes,  and  become 
fatigued.  Up  to  a  certain  point  brain  activity  is  condu- 
cive to  health,  but  if  too  long  continued  or  too  severe, 
the  cells  may  be  so  injured  that  ordi- 
nary rest  and  sleep  cannot  restore 
them.  Fatigue  is  due  (i)  to  the  con- 
sumption of  the  foods  stored  in  the 
cells  and  lymph,  which  causes  the 
cells  themselves  to  shrink  in  size  and 
become  rather  irregular  in  outline, 
and  (2)  to  the  formation  of  poisonous 
wastes  that  accumulate  in  the  cells 
and  in  the  blood.  The  brain  centers 
may  be  so  poisoned  by  the  waste 
products  that  one  does  not  realize  how 
fatigued  he  really  is.  Unless  these 
wastes  are  removed,  the  cells  repaired, 
and  new  foods  stored  up  for  future 
use,  the  brain  may  become  perma- 
Food,  oxygen,  rest,  and  sleep  must 
alternate  with  periods  of  activity  if  we  would  keep  our 
bodies  in  a  healthy  condition. 

Mental  overwork  is  possible.  Frequently,  however, 
the  real  cause  is  not  the  amount  of  work  actually  accom- 
plished, but  the  conditions  under  which  it  is  done.  If  a 


FIG.  132.  —  Showing 
changes  in  a  nerve 
cell  due  to  fatigue. 
A,  resting ;  B,  stim- 
ulated one  hour; 
C,  stimulated  six 
and  one  half  hours. 
(From  Hodge.) 

nently  injured. 


xvn      CARE  AND  TRAINING  OF  THE  NERVOUS  SYSTEM 


245 


person  insists  on  studying  immediately  after  a  full  meal, 
when  the  blood  should  go  to  the  stomach  instead  of  to 
the  brain,  indigestion,  so  common  among  brain  workers, 
must  be  the  result.  The  head  and  the  stomach  cannot 
be  active  at  the  same  time  without  bringing  on  serious 
disturbances.  Mental  work  should  be  done  when  the 
brain  has  been  repaired  and  refreshed.  The  morning 
is  the  best  time  to  study.  During  the  day  the  mental 


2Ci, 


ISO 


\ 


FIG.  133.  —  Showing  how  the  ability  to  do  physical  work  varies  from  hour  to 
hour  during  the  school  day.  The  numbers  at  the  top  represent  the  hours 
from  8  A.M.  to  4  P.M.,  and  the  numbers  at  the  left,  units  of  work.  (From 
"  Report  on  Child  Study  Investigation  in  Chicago,"  by  Dr.  Christopher.) 

powers  slowly  decline  in  vigor,  being  low  late  in  the 
forenoon,  and  again,  late  in  the  afternoon.  After  sup- 
per there  may  be  a  slight  increase  in  power  due  to  the 
nourishment  taken,  but  the  waste  products  are  still  in 
the  blood  and  interfere  with  mental  work  of  a  high 

order. 

"  Early  to  bed  and  early  to  rise, 
Makes  a  man  healthy,  wealthy,  and  wise." 


246  HUMAN  PHYSIOLOGY  CHAP. 

Physicians  tell  us  that  grief,  anxiety,  and  worry  are 
common  causes  of  a  nervous  breakdown.  A  few  years 
ago  there  was  formed  in  this  country  the  "  Don't  Worry 
Society,"  which  now  numbers  in  its  membership  hundreds 
of  brain  workers  from  all  professions.  One  of  the  very 
best  ways  to  prevent  worrying  is  to  keep  the  brain  and 
the  body  in  general  in  a  healthy  working  order.  Have 
pleasant  and  interesting  work  to  do  ;  take  a  delight  in 
doing  whatever  falls  to  your  lot ;  and  find  a  few  min- 
utes each  day  for  quiet  and  perfect  relaxation  of  every 
muscle. 

168.  Rest  and  Sleep.  —  While  exercise  is  necessary  to 
the  growth  and  development  of  the  brain,  it  must  be 
followed  by  periods  of  rest  and  sleep.  By  rest  we  may 
mean  either  complete  relaxation  of  mind  and  body  from 
all  forms  of  mental  and  physical  exertion,  or  simply  a 
change  of  employment.  The  latter  is  by  far  the  more 
important.  After  one  kind  of  physical  labor  another 
may  be  restful,  and  after  mental  work  physical  exercise 
usually  proves  very  refreshing.  This  is  because  when 
certain  brain  centers  have  been  active  for  a  time  they 
may  be  rested  by  calling  other  centers  into  activity. 
But  the  waste  products  formed  by  the  working  cells  go 
on  accumulating  in  the  blood  and  must  in  time  give  rise 
to  fatigue  and  complete  exhaustion. 

The  wastes  in  the  blood,  together  with  the  change  in 
the  circulation  to  the  brain  after  a  period  of  exercise, 
are  the  causes  of  natural  sleep.  Sleep  is  the  great 
reparative  agent  for  the  tired  and  fatigued  brain  cells. 
During  sleep  respiration  is  decreased,  the  heart  beat  is 


xvn      CARE  AND  TRAINING  OF  THE  NERVOUS  SYSTEM      247 

slower,  the  temperature  falls  a  little,  and  the  activity  cf 
all  the  cells  is  at  a  minimum.  But  certain  very  impor- 
tant changes  occur  that  make  sleep  absolutely  necessary 
to  life  and  health.  Let  us  see  what  they  are.  (i)  The 
heart,  lungs,  and  certain  other  organs  are  at  work  all 
night,  slowly  removing  from  the  cells  and  the  blood  the 
waste  products  accumulated  during  the  day.  (2)  The 
brain  cells  are  repaired  so  as  to  render  them  more 
responsive  to  the  sensory  impressions  or  stimuli  that  are 
carried  to  them.  (3)  The  cells  are  supplied  with  an 
abundance  of  food  material  for  future  use.  (4)  Not 
only  the  brain,  but  all  the  organs  and  tissues  of  the  body 
are  renovated,  repaired,  and  stored  with  energy-yielding 
materials.  Of  course  these  changes  can  occur  only 
when  the  blood  contains  an  abundance  of  nutritious 
food  stuffs  and  an  ample  supply  of  oxygen. 

The  amount  of  sleep  required  varies  with  age,  occupa- 
tion, and  conditions  of  health,  and  may  depend  some- 
what on  personal  habits.  The  adult  needs  about  eight 
hours  in  every  twenty-four  for  sleep,  while  the  child 
under  five  should  have  at  least  twelve  hours.  The  brain 
worker  needs  a  little  more  than  the  laboring  man. 
Sleep  should  be  taken  at  the  same  time  every  day.  If 
for  any  reason  the  person  does  not  get  the  required 
amount  of  sleep,  it  shows  itself  in  both  mental  and 
muscular  work.  For  children  and  youths  loss  of  sleep 
is  a  very  serious  matter,  because,  as  long  as  they  are 
growing,  all  the  cells  of  the  body  are  laying  up  a  supply 
of  energy  for  all  future  years. 

Some  persons  find  it  difficult  to  go  to  sleep,  and  resort 


248  HUMAN   PHYSIOLOGY  CHAP. 

to  artificial  measures  to  induce  sleep.  For  most  persons, 
physical  or  mental  exercise  is  sufficient  to  cause  sound 
and  natural  sleep.  Those  who  are  troubled  with  insomnia 
will  find  simple  suggestions  like  the  following  helpful :  — 

1.  Never  go  to  bed  hungry.    If  the  stomach  is  empty, 
eating  a  piece  of  bread  and  butter,  or  crackers,  or  drink- 
ing a  glass  of  milk  may  help  you  to  go  to  sleep. 

2.  Some  persons  find  a  warm  bath   taken   leisurely 
just  before  retiring  very  helpful. 

3.  Ta^e   moderate    outdoor   exercise    of    some   kind 
before  retiring. 

4.  Sleep  in  a  cool,  well-ventilated  room,  on  a  hard 
bed,  with  light  covers. 

5.  Spend  considerable  time  in  getting  ready  to  go  to 
bed,  but  be  careful  to  keep  the  feet  warm. 

6.  Do  not  review  the  events  of  the  day  after  going 
to  bed.     Better  seek  to  quiet  the  mind  by  thinking  of 
pleasant  monotonous  themes,  repeating  poetry,  counting 
your  respirations,  or  still  better  by  giving  the  stomach 
something  to  do,  as  suggested  above. 

7.  If  the  sleeplessness  comes  from  digestive  disorders, 
the  diet  should  be  carefully  looked  after. 

8.  Prolonged  insomnia  is  a  serious  matter  and  should 
be  treated  by  a  skillful  physician. 

9.  Going  to  bed  at  the  same  hour  every  night  and 
getting  up  at  a  regular  time  often  cures  cases  of  insom- 
nia.    Regularity  in  all  personal  habits  is  important  to 
good  health. 

169.   Alcohol.  —  We  have  already  seen  how  alcoholic 
beverages  inflame  the  stomach  and  intestines  and  cause 


xvn     CARE  AND  TRAINING  OF  THE  NERVOUS  SYSTEM       249 

indigestion  ;  how  they  harden  the  liver  tissue  and  impair 
its  function ;  how  they  dilate  the  capillaries  of  the  skin 
and  disturb  the  action  of  the  sweat  glands,  and  increase 
the  loss  of  heat ;  how  they  harden  the  kidney  tissues ; 
how  they  overstimulate  the  muscles,  heart,  and  arteries, 
and  so  weaken  them  and  impair  their  functions;  how 
they  diminish  the  size  of  the  air  sacs  of  the  lungs  and 
so  decrease  the  breathing  capacity ;  and  how  they  lead 
to  a  loss  of  appetite  for  nutritious  foods,  and  create  a 
craving  for  a  constantly  increasing  quantity  of  alcohol 
to  satisfy  the  abnormal  appetite.  But  the  soft  and  deli- 
cate nerve  tissue  of  which  the  brain  and  nerves  are 
composed  are  affected  more  profoundly  than  any  other 
tissue,  and  perhaps  more  than  all  other  organs  put  to- 
gether. The  delicate  nerve  tissue  undergoes  two  impor- 
tant changes :  first,  the  protoplasm  of  the  cell  body  and 
of  the  fiber  are  in  part  destroyed ;  and  second,  connec- 
tive tissue  and  fat  are  deposited  in  the  cell  and  take  the 
place  of  the  destroyed  protoplasm.  These  changes  in 
structure  are  accompanied  by  many  disturbances  in  the 
activities  of  the  nerve  cells. 

The  moral  sense  is  perhaps  the  first  to  suffer  from 
the  effects  of  alcohol,  then  the  will  power  is  lost,  and 
finally  the  intellectual  activities  are  impaired.  In  writ- 
ing of  the  person  who  habitually  uses  alcoholic  bever- 
ages, Dr.  Madden  says :  "  Sense  of  dignity,  of  honor,  of 
moral  obligations,  of  personal  conduct,  no  longer  move 
him  as  formerly.  He  thinks  only  of  escaping  from 
them.  It  is  a  well-known  fact  that  the  will  power  is 
early  and  profoundly  affected  in  alcoholism,  The  sub- 


250  HUMAN  PHYSIOLOGY  CHAP. 

ject  loses  the  power  to  control  his  own  actions,  and  he 
is  willing  to  be  led  by  very  slight  influences.  Last  to 
fail,  as  a  rule,  is  intellectual  power.  It  may  show  itself 
after  prolonged  excessive  indulgence,  even  after  the 
body  is  become  a  wreck.  Sometimes  it  is,  in  a  fitful 
way,  present  to  the  last.  The  drunkard  is  indifferent 
to  all  social  and  other  questions  which  give  interest  to 
the  lives  and  intercourse  of  the  healthy.  His  conversa- 
tion is  broken  and  his  ideas  fragmentary.  Finally,  the 
memory  fails  in  a  marked  degree,  and  he  soon  reaches 
a  stage  of  mental  degeneration  which  renders  him  unfit 
for  any  useful  calling." 

The  relation  of  the  use  of  alcoholic  beverages  to 
poverty,  crime,  suffering,  immorality,  debauchery,  and 
insanity  is  too  well  known  to  require  any  special  dis- 
cussion here.  It  is  believed  that  alcoholism  in  the 
parent  is  often  the  cause  of  feeble-mindedness,  epilepsy, 
and  nervous  disorders  of  all  kinds  in  the  offspring. 
Dr.  Frick  of  Zurich  says  that  about  fifty  per  cent  of 
the  inmates  of  institutions  for  feeble-minded  children, 
for  epileptics,  and  for  deaf  mutes  are  the  children  of 
drinking  parents. 

170.  Tobacco.  —  Tobacco,  whether  chewed,  snuffed, 
or  smoked  in  a  pipe,  cigar,  or  cigarette,  contains  a  nar- 
cotic poison  called  nicotine  which  has  an  injurious  effect 
upon  the  nervous  system,  especially  of  the  young.  It 
stunts  the  growth  of  the  body  as  a  whole,  irritates  and 
weakens  the  nervous  system,  makes  the  user  cross  and 
peevish,  and  unfits  him  for  the  best  society.  Upon  the 
adult  the  effect  may  be  less  marked,  and  yet  the  use  of 


xvii      CARE  AND  TRAINING  OF  THE  NERVOUS  SYSTEM      251 

tobacco  must  be  looked  upon  as  a  useless  and  expensive 
habit. 

Opium,  chloral,  and  other  similar  drugs  contain  nar- 
cotic poisons,  and  should  never  be  used  by  either  young 
or  old  unless  prescribed  by  a  reputable  physician  and 
taken  under  his  direction.  The  moral  effect  of  the  use 
of  these  narcotics  may  be  even  greater  than  that  of 
alcohol.  The  only  safe  rule  for  a  long,  healthy,  useful, 
and  happy  life  is  never  to  touch  any  of  these  drugs. 


SUMMARY   OF  THE   MAIN   POINTS 

1.  One  eighth  of  all  the  blood  is  used  by  the   brain.     It 
requires  a  large  quantity  of  nutritious  food  and  pure  air  to  keep 
the  brain  in  a  good,  healthy,  working  condition. 

2.  The  brain  cells  should  be  used  regularly  and  systematically 
in  a  large  variety  of  exercises,  so  as  to  call  into  action  all  the 
different  centers. 

3.  When  nerve  cells  function  they  consume  food  material, 
produce  waste  products,  and  become  fatigued. 

4.  Worry,  anxiety,  and  grief  are  probably  more  frequently 
the  cause  of  a  nervous  breakdown  than  mental  work. 

5.  Change  of  occupation  is  restful  because  new  nerve  centers 
are  called  into  action,  hence  we  should  not  continue  too  long  at 
the  same  task. 

6.  Natural  sleep  is  nature's  most  powerful  reparative  agent. 
The  wastes  are  removed,  and  the  cells  repaired  and  stored  with 
new  energy-yielding  materials. 

7.  An  infant  sleeps  most  of  the  time,  a  child   under  five 
requires  about  twelve  hours,  an  adult  about  eight.     The  brain 
worker  needs  a  little  more  sleep  than  the  laboring  man. 

8.  Regular  habits  of  sleeping  are  just  as  important  as  a  regu- 


252  HUMAN  PHYSIOLOGY  CHAP,  xvn 

lated   life   in    other   matters.     Sleeping,   eating,   and   working 
should  all  be  carefully  regulated  as  to  time  and  amount. 

9.  Education  is  designed  to  exercise  and  develop  all  the 
brain  cells,  and  to  create  a  wide  range  of  sympathies  and  inter- 
ests in  early  life. 

10.  When  brain  cells  act  they  become  so  changed  as  to  make 
it  easier  to  act  the  same  way  a  second   time.     This  we   call 
habit.     Habits  are  due  to  changes  in  the  brain  structure. 

11.  The  two  important  principles  are  :    (i)  Habits  are  most 
easily  formed  in  early  life.      (2)  Habits  are  most  easily  formed 
during  periods  of  rapid  growth  and  great  nutrition. 

12.  Good   habits  become  our  strongest  friends  and  allies, 
while  bad  habits  are  our  worst  enemies  and  most  hostile  foes. 

13.  Alcohol  affects  the  nerve  tissues  more  profoundly  than 
the  other  tissues.     It  tends  to  destroy  the  cell  protoplasm  and 
increase  the  amount  of  connective  tissue  and  fat. 

14.  Alcohol  weakens    the    moral    sense,   destroys  the  will, 
impairs    the   intellect,    and   causes   poverty,    crime,    suffering, 
immorality,  debauchery,  and  insanity. 

15.  Tobacco  and  other  narcotic  drugs  are  harmful  to  the 
nervous  system,  and  should  never  be  used  unless  prescribed  by 
a  reputable  physician. 


CHAPTER   XVIII 

THE   SPECIAL   SENSES   AND   SENSATIONS 

171.  Sensations. — We  have  learned  that  the  general 
plan  of  the  nervous  system  is  to  have  nerves  run  to  the 
brain  and  spinal  cord,  which  convey  impressions  from 
all  parts  of  the  body  to  the  central  organs,  and  then 
another  class  of  nerves  to  convey  messages  issued  by 
the  central  organs  to  the  muscles  and  glands  in  all 
parts  of  the  body.  The  first  are  sensory  nerves  and  the 
second  motor  nerves.  In  this  chapter  we  shall  study 
the  organs  from  which  the  sensory  nerves  start,  and 
learn  what  the  brain  does  with  the  impressions  which  it 
receives. 

The  brain  receives  impressions,  and,  in  some  way 
not  understood  by  scientists,  gives  them  meaning.  We 
say  the  mind  has  the  power  to  interpret  these  impres- 
sions or  transform  them  into  sensations.  Every  sen- 
sory nerve,  whether  from  the  eye  or  stomach,  the  ear 
or  lungs,  the  tongue  or  toes,  brings  impressions  from 
which  we  gain  a  knowledge  of  our  own  bodies  and  of 
the  world  about  us.  The  moment  an  object  comes  in 
contact  with  the  hand,  certain  little  organs  in  the  skin 
receive  the  impressions,  and  nerves  carry  these  impres- 
sions to  the  sensory  areas  of  the  brain,  and  we  become 

253 


254  HUMAN   PHYSIOLOGY  CHAP. 

aware  of  the  object.      We  become  conscious  of  a  sensa- 
tion. 

172.  General   Senses.  —  Many   sensory   nerves    come 
from   the  internal   organs,  as   the  stomach,  intestines, 
lungs,  kidneys,  heart  and  blood  vessels,  liver,  etc.     They 
give  us  sensations  of  hunger,  thirst,  faintness,  giddiness, 
discomfort,  fatigue,  itching,  burning,  aching,  shudder- 
ing, creeping,  and  the  like.     These  sensations  do  not 
bring  us  any  information  of  the  objects  about  us,  but 
they  do  tell  us  something  of  the  conditions  of  the  vari- 
ous organs.    They  tell  us  when  we  are  to  eat  and  drink, 
when  we  are  tired  and  sick,  when  we  need  sleep  and 
exercise,  and  a  thousand  other  things  important  to  health 
and  happiness. 

There  are  no  special  structures  from  which  these 
nerves  start.  They  begin  in  free  nerve  endings  and 
give  us  general  or  common  sensations.  All  other  sen- 
sory nerves  come  from  the  eyes,  ears,  nose,  mouth,  and 
skin,  and  give  us  the  special  sensations.  We  shall  now 
study  the  special  sense  organs. 

173,  The  Sense  of  Touch. — The  true  skin  has  little 
projections  called    papilla,   quite   close   together.       In 
these    papillae   there  are    peculiar   little  end  organs  in 
which  sensory  nerves  of  touch  begin.    These  end  organs 
occur  in  the  tongue,  in  the  mucous  membrane  of  the 
mouth  and  lips,  and  in  the  skin  all  over  the  body ;  they 
enable  us  to  feel.     They  are  most  numerous  on  the  tip 
of  the  tongue  and  in  the  ends  of  the  fingers,  and  fewest 
on  the  middle  of  the  back. 

When  these  end  organs  are  stimulated  by  objects,  we 


XVIII 


THE   SPECIAL   SENSES  AND    SENSATIONS 


255 


get  sensations  of  rough  and  smooth,  wet  and  dry,  soft 
and  hard,  and  hot  and  cold.  In  the  muscles,  joints,  and 
tendons,  similar  "  touch  bodies  "  are  found  which  give 
us  sensations  that  make  muscular  contractions  accu- 
rate, and  balancing, 
standing,  and  walk- 
ing possible. 

The     sense     of  ^p       am         JT   B 

A  '* '  *W 

touch  may  be 
highly  developed 
by  regular  exercise. 
The  blind  read  by 
passing  the  fingers 
over  slightly  raised 
letters  or  points. 
They  distinguish 
their  friends  and 
all  objects  about 
them  by  the  touch. 
The  quality  of  paper,  silks,  and  other  fabrics  is  deter- 
mined by  expert  buyers  very  largely  through  the  sense 
of  touch. 

1.  Blindfold  a  member  of  the  class  and  touch  different  parts  of 
his  body.     Ask  him  to  locate  accurately  the  part  touched. 

2.  Touch  the  palm  of  the  hand  with  a  colored  pencil  and  have 
him  find  the  exact  point  with  another  pencil.     Measure  the  distance 
between  the  two  points.    Repeat  this  several  times  on  the  same  part 
of  the  body. 

3.  Try  different  parts  of  the  body  in  the  same  way. 

4.  With  the  points  of  a  pair  of  scissors  slightly  separated  touch 
the  tip  of  the  index  finger.     How  far  apart  can  you  feel  the  points 
as  two  when  placed  on  the  skin  at  the  same  time  ? 


FIG.  134.  —  Different  kinds  of  touch  bodies. 
A,  from  the  cornea  of  the  eye ;  B,  from  the 
tongue  of  the  duck ;  and  C,  D,  E,  from  the 
skin  of  the  fingers.  (Drawn  by  Zinns.) 


256 


HUMAN    PHYSIOLOGY 


CHAP. 


5-  Try  the  palm,  the  back  of  the  hand,  the  forearm,  the  elbow, 
the  tip  of  the  tongue,  the  back  of  the  neck,  etc. 

6.  Cross  your  middle  finger  over  the  forefinger  of  the  same  hand 
and  touch  the  tip  of  the  tongue  to  the  crossed  ends.  What  sensation 
results  ?  In  the  same  way,  touch  the  point  of  the  nose. 

174.  The  Sense  of  Taste.  —  The  tongue  is  the  princi- 
pal organ  of  taste.  If  you  examine  the  upper  surface 
of  the  tongue  carefully,  three  different  kinds  of  papillae 

will  be  found.  On 
the  back  part  of 
the  tongue  there 
are  from  seven  to 
eleven  rather  large 
circular  papillae. 
On  the  tip  and 
sides  the  papillae 
are  slender,  and 
when  largely  de- 
veloped, as  in  the  cow  and  cat,  they  give  a  roughness 
to  the  tongue.  Papillae  of  a  third  class  are  scattered 
over  the  tongue  among  the  others.  There  are  papillae 
on  the  tongue,  soft  palate,  and  pharynx.  In  the  papillae 
occur  little  structures  known  as  taste  buds  in  which  the 
nerves  of  taste  begin.  The  taste  buds  are  sensitive  to 
sweet,  sour,  bitter,  and  salt.  These  are  the  chief  sensa- 
tions of  taste.  It  is  interesting  to  know  that  the  tip  of 
the  tongue  is  most  sensitive  to  sweet,  and  the  back  of  the 
tongue  to  bitter.  No  substance  can  be  tasted  until  it 
has  been  dissolved  and  some  of  the  solution  comes  in  con- 
tact with  the  nerve  endings  in  tJie  taste  buds. 


FIG.  135.  —  The  tongue,  showing  the  nerves  of 
taste  and  the  papillae.     (Drawn  by  Zuppke.) 


XVIII 


THE   SPECIAL   SENSES  AND    SENSATIONS 


257 


Taste  guides  us  in  the  selection  of  foods  and  gives 
an  added  pleasure  to  eating.  It  may  be  highly  culti- 
vated by  constant  practice,  as  is  shown  in  expert  tea 
tasters  and  French  epicures. 

1 .  Rub  your  hand  over  a  cat's  tongue  and  notice  how  rough  it 
feels.     Compare  with  a  cow's  tongue. 

2.  Put  a  drop  of  vinegar  on  the  back,  on  the  tip,  and  on  the 
sides  of  the  tongue.     Which  is  most  sensitive  ? 

3.  In  the  same  way  try  a  bit  of  sugar,  a  little  salt,  and  some 
quinine. 

4.  What  do  you  learn  from  exercises  2  and  3  ?     Explain. 

175.  The  Sense  of  Smell.  —  The  mucous  membrane 
of  the  nasal  cavities  contains  the  sensitive  ends  of  the 
nerves  of  smell. 
They  are  most 
numerous  in  the 
upper  half  of  the 
nasal  cavities,  and 
are  quite  removed 
from  the  direct 
current  of  air  that 
constantly  passes 
through  the  nose 
in  breathing.  That 


is  why  we  "  sniff 
and  smell  "  to  de- 
tect a  faint  odor. 

Any    substance 
that  can  excite  the  nerve  of  smell  gives  off  to  the  air 
very  fine  particles,  called  effluvia.    The  particles  dissolve 


FlG.  136.  —  The  outer  wall  of  the  left  nasal  cav- 
ity. /,  the  nerve  of  smell  and  its  branches; 
V,  V,  cranial  nerve;  ST,  MT,  and  IT,  tur- 
binate  bones;  and  Pa,  hard  palate.  (From 
Huxley.) 


258  HUMAN   PHYSIOLOGY  CHAP. 

on  the  moist  mucous  surface  in  the  nose,  and  then  stimu- 
late the  end  organs  of  smell.  The  sense  of  smell  aids 
us  in  the  selection  of  good  foods  and  in  the  avoidance 
of  bad  air.  In  some  of  the  lower  animals,  as  the  blood- 
hound, for  example,  this  sense  is  much  more  highly 
developed  than  in  man. 

Taste  and  smell  are  so  closely  associated  that  it  is 
often  difficult  to  separate  them.  Apple  and  onion 
taste  very  differently  to  us,  but  they  taste  quite  alike  to 
the  person  who  has  lost  the  sense  of  smell.  Highly 
flavored  foods,  alcohol,  and  tobacco  tend  to  blunt  these 
senses. 

1.  Blindfold  a  member  of  the  class,  and  pinch  his  nostrils  firmly, 
and  then  have  him  try  to  distinguish  between  apple,  potato,  and 
onion  by  the  sense  of  taste. 

2.  Chew  some  roasted  coffee  and  notice  carefully  the  taste  and 
odor.     Repeat,  but  pinch   the  nostrils  firmly  all  the  time.     What 
difference  do  you  observe  ?    .When  a  person  has  a  cold  in  the  head 
some  foods  are  tasteless.     Can  you  tell  why  ? 

176.  The  Sense  of  Hearing.  —  We  come  now  to  con- 
sider one  of  the  most  important  senses  in  man.  How 
dreary  and  gravelike  the  world  would  seem  if  we  could 
not  hear  the  song  of  the  birds,  the  hum  of  the  bees, 
and  the  voices  of  our  friends !  The  sense  of  hearing 
can  receive  the  waves  of  air  caused  by  the  vibrations  of 
a  sounding  body  and  give  them  meaning.  What  is 
sound  ?  We  shall  try  to  find  out.  The  vocal  cords  of  a 
person  vibrate  as  the  air  is  forced  out  of  his  lungs,  and 
produce  a  wavelike  disturbance  in  the  air.  Between  his 
lips  and  your  ear  there  are  waves  of  air  which  you  can 
interpret,  and  so  understand  what  he  says. 


XVIII 


THE   SPECIAL   SENSES   AND   SENSATIONS 


259 


The  organ  of  hearing  is  the  ear.  It  has  a  very  com- 
plicated structure,  but  we  shall  try  to  understand  the 
different  parts,  and  see  how  they  work.  The  three 
parts  of  the  ear  are  known  from  their  location  as  the 
external,  the  middle,  and  the  inner  ear. 

177.  The  External  Ear.  —  This  consists  of  two  parts. 
The  first  is  an  irregular  shell  of  cartilage  or  gristle,  cov- 
ered with  skin,  that 
projects  from  either 
side  of  the  head.  It 
serves  as  a  funnel  to 
catch  the  waves  of  air 
and  to  direct  them  to 
the  middle  ear.  The 
second  is  the  audi- 
tory canal,  which  is 
about  one  inch  long 
and  arched  upward 
slightly  near  the  mid- 
dle. It  extends  to  the 
middle  ear  and  serves 
to  conduct  the  sound 
waves  to  the  eardrum. 

The  auditory  canal  consists  of  cartilage  and  bone 
covered  with  skin.  On  the  outer  two  thirds  occur 
small  glands  that  secrete  earwax  or  cerumen.  This  is 
a  yellowish  sticky  fluid  that  soon  unites  with  some  of 
the  thin  scales  of  the  epidermis,  and  hardens  to  a  pasty 
consistency.  The  wax  has  a  bitter  taste  and  serves  to 
keep  insects  out  of  the  ear,  to  moisten  the  parts  of  the 


Concha 


FIG.  137,  —  The  external  ear  (Cheever). 


260  HUMAN   PHYSIOLOGY  CHAP. 

canal,  and  to  remove  the  little  flakes  of  epidermis  as 
they  scale  off.  In  a  healthy  ear  there  is  very  little 
wax  and  one  never  needs  to  remove  it.  Sometimes, 
however,  it  may  collect  in  the  ear  and  interfere  with  the 
free  movement  of  the  eardrum.  It  must  then  be  care- 
fully removed  by  a  skillful  aurist. 

178.    The  Middle  Ear.  —  This  consists  of  a  thin  mem- 
brane,   the   drumhead,    stretched    across    the    auditory 

canal  as  its  outer  boundary. 
It  is  this  membrane  that  vi- 
brates in  order  to  enable  us  to 
hear.  If  the  earwax  should 
accumulate  on  the  outer  sur- 
face of  the  drumhead,  or  if  the 
drumhead  should  be  punc- 
tured, we  could  not  hear  so 

FIG.  138.-  The  chain  of  bones        well«       Just   beyond    the    drum- 

of  the  middle  ear.    (Drawn      head  is  a  chain  of  three  small 

by  Johnstone.)  .  i  •    i     v    «j 

bones  which  bridges  the  cavity 

of  the  middle  ear.  The  malleus  is  attached  to  the  center 
of  the  drum  by  means  of  its  long  handle,  the  anvil 
joins  the  round  head  of  the  malleus  with  the  small  end 
of  the  stapes,  and  the  large  end  of  the  stapes  fits  into 
an  opening  of  the  inner  ear,  called  the  oval  window. 
These  three  bones  are  so  shaped  and  fastened  together 
that  they  transmit  the  sound  waves  to  the  internal  ear 
precisely  as  they  receive  them,  except  that  the  waves 
are  focused  on  a  smaller  area  and  much  intensified. 
The  Eustachian  tube  extends  from  the  cavity  of  the 
middle  ear  down  to  the  pharynx,  and  keeps  the  air 


XVIII 


THE   SPECIAL  SENSES  AND   SENSATIONS 


261 


pressure  the  same  on  the  inner  and  outer  surfaces  of 
the  drumhead.  This  tube  and  the  entire  middle  ear 
are  lined  with  mucous  membrane.  Hence,  it  is  easily 
seen  why  a  cold  in  the  head,  sore  throat,  catarrh,  and 
adenoid  growths  affect  our  hearing.  Anything  that 
tends  to  close  the  Eustachian  tubes  or  to  obstruct  the 
air  passages  makes  the  drumhead  less  sensitive  to  sound 
waves  and  impairs  hearing. 

Close  the  mouth,  pinch  the  nostrils  firmly,  and  then  swallow. 
Because  a  little  air  is  removed  from  the  pharynx  the  eardrum  is 
pushed  in,  causing  the  peculiar  cracking  sound. 

179.  The  Inner  Ear.  —  There  is  no  more  delicate  or 
complicated  organ  in  the  body  than  the  inner  ear,  which 
is  the  real  end  organ 
of  hearing.  It  con- 
sists of  a  series  of 
winding  passages  in 
the  temporal  bone, 
and  may  be  divided 
into  three  parts  :  the 
small  vestibule  next 
to  the  middle  ear 
with  which  the  stapes 
communicates  ;  the 
three  semicircular  canals  or  winding  passages  connected 
with  the  vestibule  behind  and  above ;  and  the  cochlea  or 
snail  shell  joined  to  the  vestibule  on  the  opposite  side, 
in  front  and  below.  All  these  parts  are  filled  with  a 
liquid  called  perilymph,  in  which  floats  a  saclike  mem- 
brane, the  membranous  labyrinth,  that  has  about  the 


FIG.  139.  —  The  inner  ear,  showing  the  shape  of 
the  bony  labyrinth  (Zuppke). 


262 


HUMAN   PHYSIOLOGY 


CHAP. 


same  shape  as  the  bony  labyrinth.     Within  the  sac  is 
another  liquid  called  endolymph. 

The  auditory  nerve,  as  the  nerve  of  hearing  is  called, 
has  fibers  going  to  each  of  the  semicircular  canals,  to 
the  vestibule,  and  to  all  parts  of  the  cochlea,  where  they 
spread  out  on  the  surface  of  the  membranous  labyrinth. 
The  sound  waves  come  in  contact  with  the  fibers  of  the 
auditory  nerve  ;  but  only  those  distributed  to  the  cochlea, 


FIG.  140.  —  A  section  through  the  ear.     (From  Boas  by  Zuppke.) 

which  is  the  most  important  part  of  the  ear,  are  used  in 
hearing.  Those  of  the  semicircular  canals  and  the 
vestibule  carry  to  the  brain  impressions  that  enable  us 
to  judge  of  the  position  of  the  body  in  space  and  help 
to  keep  us  right  side  up.  We  become  dizzy  if  we  swing 
about  in  a  circle  for  a  short  time.  This  is  because  the 
liquid  in  the  canals,  which  acts  like  a  carpenter's  level, 
is  disturbed  by  the  rotation  of  the  body.  The  feeling 
of  nausea  and  sickness  that  some  persons  experience 
from  riding  on  a  boat,  train,  street  car,  or  carriage,  and 


xvni  THE   SPECIAL   SENSES  AND   SENSATIONS  263 

sometimes  from  swinging  in  a  hammock,  is  due  to  the 
same  cause. 

180.  The  Course  of  a  Sound  Wave.  —  The  cartilaginous 
funnel  or  concha  of  the  external  ear  catches  sound 
waves  and  directs  them  into  the  auditory  canal,  which 
conveys  them  to  the  drumhead.  The  sensitive  membrane 
of  the  drumhead  responds  to  the  waves  and  vibrates 
like  the  diaphragm  of  the  telephone.  These  vibrations 
are  transmitted  to  the  chain  of  bones  of  the  middle  ear, 
which  modify,  intensify,  and  focus  the  motion  upon  the 
membrane  stretched  across  the  oval  window  of  the 
internal  ear,  into  which  the  base  of  the  stapes  fits. 
The  vibrations  of  the  oval  window  set  in  motion  both 
the  perilymph  of  the  bony  labyrinth  and  the  endolymph 
within  the  membranous  sac.  The  waves  enter  the 
vestibule,  pass  through  the  semicircular  canals  and  the 
entire  cochlea,  and  back  to  the  vestibule,  where  they  pass 
into  the  middle  ear  at  the  round  window.  The  motion 
of  the  liquids  causes  the  membranous  sac  to  vibrate, 
and  this  vibration  irritates  the  delicate  nerve  endings. 
These  nerve  impressions  are  carried  to  the  proper  cen- 
ters in  the  brain,  and  we  hear.  What  a  complicated 
process  hearing  is ! 

1.  Hold  a  watch  between  the  lips  for  a  moment,  and  then  close 
the  teeth  down  on  it  and  notice  how  loud  it  seems  to  tick. 

2.  Cover  both  ears  and  then  uncover  one  and  notice  the  result. 
Repeat  several  times.     Explain. 

3.  Hold  a  vibrating  tuning  fork  between  the  lips  until  it  can  no 
longer  be  heard.     Close  the  teeth  down  on  it  and  it  will  be  heard 
again.     When  it  can  no  longer  be  heard  the  second  time,  cover  one 
or  both  ears  and  it  will  be  heard  a  third  time.     Explain. 


264  HUMAN   PHYSIOLOGY  CHAP. 

181.  Care  of  the  Ear.  —  The  delicate  parts  of  the  ear 
are  well  protected  and  need  very  little  attention.  Even 
the  outer  ear,  if  in  perfect  health,  needs  only  to  be  kept 
clean.  The  auditory  canal  requires  no  care  whatever 
except  to  remove  the  wax  as  it  loosens  and  works  out. 
The  chief  caution  for  most  persons  to  remember  is  : 
Keep  the  concha  clean  and  do  not  meddle  with  the 
auditory  canal. 

If  there  is  "running"  from  the  ear,  or  if  the  wax 
accumulates  on  the  eardrum  so  as  to  impair  hearing, 
you  should  consult  an  aurist  at  once.  No  pin,  pencil,  or 
toothpick  should  be  used  to  loosen  the  wax  or  to  clean 
the  canal,  for  there  is  great  danger  of  scratching,  tearing, 
or  puncturing  the  drumhead.  If  a  foreign  substance 
gets  into  the  ear  and  cannot  be  easily  removed,  a  doctor 
should  be  consulted  at  once.  Sometimes  a  bug,  ant,  or 
other  small  insect  crawls  into  the  auditory  canal.  A 
light  held  close  to  the  ear  while  the  canal  is  straightened 
by  pressing  up  the  outer  end  may  coax  the  insect  to  crawl 
out.  If  it  does  not  come  out  soon  or  cease  irritating  the 
ear,  it  should  be  smothered  by  dropping  in  a  little  tepid 
water  or  sweet  oil.  A  dead  insect  or  a  small  foreign 
object  may  do  little  harm  even  if  not  removed  for  years. 
Most  harm  comes  from  the  attempt  to  remove  it.  Small 
objects  will  often  drop  out  at  once  if  the  part  in  front 
of  the  ear  is  rubbed  in  a  rotary  manner  while  the  head 
is  turned  to  the  side. 

Impaired  hearing  and  deafness  may  be  the  result  of 
scarlet  fever,  mumps,  diphtheria,  adenoid  growths,  colds, 
catarrh,  a  sudden  blow  on  the  head,  loud  noises,  certain 


xvi ii  THE   SPECIAL   SENSES   AND   SENSATIONS  265 

drugs,  and  many  other  causes.  A  person  may  suffer 
from  defective  hearing  without  being  aware  of  it  at  all. 
It  is  important  to  test  the  ears  of  children  by  some 
simple  method,  as  seeing  how  far  they  can  hear  the 
ticking  of  a  watch  with  each  ear  separately. 

Blindfold  a  person  and  cover  one  ear,  and  then  hold  a  ticking 
watch  close  to  the  other  ear.  Carry  it  away  slowly  and  determine 
how  far  it  can  be  heard.  Repeat  for  the  other  ear.  Are  the  two 
ears  equally  sensitive  to  sound? 

182.  The  Sense  of  Sight.  —  Sight  is  probably  the  most 
important    sense   we    have.     The    beautiful    colors    in 
nature    and  art  would  be    entirely    unknown,    and    life 
would  lose  many  of  its  pleasures,  if  we  could  not  see. 
Seeing   is    even    more    wonderful   than    hearing.      We 
learned  that  the  beautiful  music  of  an  orchestra  and 
the  sweet  voice  of  a  friend  are  simply  vibrations  of  air. 
All  objects  that  we  can  see  give  forth  vibrations  to  the 
ether.     The  beautiful  color  of  the  rose  is  simply  ether 
vibrations  that  can  act  upon  the  delicate  eye  in  such  a 
way  as  to  cause  sensations  of  sight.     The  vibrations  of 
ether  differ  from  each  other  and  thus  give  rise  to  the 
different  colors  of  the  rainbow  and  their  many  shades 
and  tints.     We  shall  now  study  the  eye  and  learn  how 
we  see. 

183.  The  Eyeball.  —  The  eyeball  is  spherical  in  shape, 
measuring  about  one  inch  from  side  to  side  and  a  little 
less  from   front  to  back.     It  is   set  in  a  bony  cavity 
called  the  orbit,  which  is  lined  by  a  mass  of  connective 
tissue    and   fat.     The   back  two   thirds   of  the   eyeball 
is  inclosed  in  a  capsule  of  serous  membrane  like  the 


266 


HUMAN    PHYSIOLOGY 


CHAP. 


pleura  and  pericardium.  The  capsule  and  cushion  of 
fat  protect  the  eyeball  and  permit  it  to  turn  freely  in  all 
directions  with  very  little  friction. 

The  eyeball  has  three  coats  or  layers.  The  outer  is  a 
firm  and  strong  coat,  white  in  color,  that  gives  the  eye  its 
shape.  The  part  at  the  back  and  sides  does  not  permit 
light  to  pass  through.  This  portion  is  called  the  sclerotic 

coat.  The  part  in 
front  is  very  trans- 
parent and  forms 
a  round  window 
known  as  the  cor- 
nea, through  which 
light  enters  the 
eye.  The  second 
or  middle  is  a  more 
delicate  though 
thicker  coat,  deep 
black  in  color,  that 
serves  to  absorb 
all  the  extra  light 
which  would  other- 
wise interfere  with  good  clear  vision.  In  this  layer  there 
are  many  blood  vessels  and  nerves.  This  coat,  known 
as  the  choroid,  has  the  little  self-regulating  curtain  just 
back  of  the  cornea,  which  by  changing  the  size  of  the 
small  opening  at  its  center,  determines  the  amount  of 
light  that  shall  enter  the  eye.  This  part  of  the  choroid 
coat  is  the  iris,  and  the  little  window  is  the  pupil.  The 
iris  gives  color  to  the  eyes,  as  it  may  be  black,  brown, 


FIG.  141.  —  A  section  through  the  eyeball 
(Zuppke). 


XVIII 


THE   SPECIAL   SENSES  AND    SENSATIONS 


267 


blue,  or  gray.  The  third  or  inner  coat  is  an  extremely 
thin  and  delicate  film  called  the  retina.  It  is  really  an 
expansion  of  the  optic  nerve  that  forms  a  sensitive  lining 
for  the  inner  surface  of  the  eyeball.  Before  an  object 
can  be  seen  it  must  form  an  image  on  the  retina. 

184.    Muscles  of  the   Eye.  — Each    eyeball   has    four 
straight  muscles  attached  to  it,  one  above,  one  below, 


FIG.  142.  —  Muscles  of  the  eyeball.  (From  Blaisdell's  "Life  and  Health." 
Ginn  &  Co.)  A,  tendon  of  three  recti  muscles;  B,  external  rectus,  cut  and 
pulled  downward;  C,  inferior  rectus;  D,  internal  rectus;  £,  superior 
rectus  ;  F,  superior  oblique ;  H,  pulley  of  the  superior  oblique  ;  K,  inferior 
oblique  ;  L,  M,  levator  palpebrae ;  -N,  optic  nerve. 

and  one  on  either  side  ;  besides  these  four  there  is  an 
oblique  muscle  attached  to  the  upper  part  of  the  eyeball 
and  one  to  the  lower.  By  means  of  these  six  muscles 
the  eye  may  be  turned  in  any  direction  without  mov- 
ing the  head  at  all. 

The  muscles  of  the  two  eyes  usually  work  in  perfect 
harmony,  so  that  the  eyes  move  together.    Sometimes  the 


268  HUMAN   PHYSIOLOGY  CHAP. 

muscles  do  not  balance  each  other  as  they  should ;  the 
inner  may  be  too  strong  for  the  outer  and  then  the  eyes 
turn  in  toward  the  nose;  this  is  called  "  cross-eyed."  If 
the  outer  muscles  are  the  stronger  the  person  is  "  wall- 
eyed." Oculists  can  cut  the  muscles  just  enough  to 
straighten  the  eyes  and  make  them  work  together  prop- 
erly. If  this  is  necessary,  it  should  be  done  in  childhood. 

1 .  Get  a  sheep's  eye  from  your  butcher  and  study  the  eyeball  as 
a  whole.     Notice  the  six  muscles  of  the  eye.     What  is  the  function 
of  each?     Notice  the  cushion  of  fat  around  the  eyeball. 

2.  Remove  the  muscles  and  fat  and  locate  the  optic  nerve,  the 
cornea,  and  sclerotic  coat. 

3.  Notice  the  size  and  shape  of  the  pupil  of  the  eye.     Find  the 
iris  and  notice  its  shape  and  color. 

4.  Remove  a  strip  of  the  sclerotic  coat,  so  that  a  portion  of  the 
choroid  may  be  exposed. 

5.  Lift  up  the  choroid  with  forceps  and  cut  through  it  carefully. 
The  delicate  retina  can  be  seen  below.     Make  drawings  in  each  case. 

185.  Appendages  of  the  Eye.  —  The  eyeball  is  set  deep 
in  the  orbit  in  order  to  protect  it  from  injury.  Besides 
this  it  is  provided  with  eyelids,  eyebrows,  eyelashes,  and 
tear  glands  to  protect,  keep  clean,  and  moisten  the  more 
exposed  parts  of  this  delicate  and  important  organ. 

The  eyelids  are  made  of  thin  plates  of  cartilage 
covered  with  skin,  and  lined  with  a  thin  mucous  mem- 
brane called  the  conjunctiva.  The  conjunctiva  also 
covers  the  front  of  the  eyeball  except  the  central  part  of 
the  cornea.  The  two  lids  may  be  brought  together  and 
thus  cover  the  eyeball  in  front,  protecting  it  against 
foreign  bodies.  They  also  distribute  moisture  over  the 
surface  of  the  cornea.  The  eyelashes  are  a  row  of  fine 


THE   SPECIAL   SENSES  AND   SENSATIONS 


269 


hairs  on  the  edge  of  each  lid.     The  hairs  have  delicate 
nerves  at  their  roots  and  so  serve  to  warn  us  against 


fyeiasties 

Sc/erof/c 


FIG.  143.  — The  left  eye  (Zinns). 

small  objects  approaching  the  eye  and  against  dust. 
The  eyebrows  protect  the  eye  against  dust  and  perspira- 
tion, and  they  give  it  shade. 

The  tear  glands  (lachrymal  glands)  are  situated 
above  and  at  the  outer  angle  of  the  eye.  They  secrete 
the  tears  and  pour  them 
out  under  the  upper  lid, 
where  they  are  distrib- 
uted over  the  eye  so  as 
to  moisten  the  entire 
cornea.  Each  lid  has  a 
small  duct  at  its  inner 
end,  into  which  the 

moisture       is       Collected          FIG.  144.-  The  lachrymal  apparatus 
-         ...  ..    ,       ,  (Zuppke). 

after  it  has  accomplished 

its  purpose.     These  two  ducts  unite  and  lead  to  the  tear 

bag  (lachrymal  sac),  from  which  a  single  duct  leads  to 


Uucfc 


270 


HUMAN   PHYSIOLOGY 


CHAP. 


the  nose.  Sometimes  this  duct  closes  up,  and  then 
tears  constantly  gather  at  the  inner  angle  of  the  eye. 
It  should  be  opened  by  an  oculist  so  that  the  tears  may 
drain  off  as  they  should. 

1.  With  a  small  mirror  examine  carefully  the  orbits  of  your  own 
eyes.     Notice  that  a  ruler  placed  on  the  bones  of  the  orbit  does  not 
touch  the  eyeball  at  all. 

2.  Study  the  eyebrows  and  notice  their  position,  and  the  direction 
and  color  of  the  hair. 

3.  Study  the  eyelids.      Notice  a  rudimentary  lid  at  the  inner 
corner  of  each  eye.     Do  you  find  an  opening  on  an  elevation  at  the 
inner  corner  of  the  lower  lid?    This  is  the  opening  into  the  lachrymal 
canal. 

186.  The  Inside  of  the  Eyeball. —  The  eyeball  is  a 
large  hollow  globe  filled  with  liquids.  The  space  just 
back  of  the  cornea  is  filled  with  aqueous  humor,  in  which 
the  iris  floats.  Beyond  this  we  find  the  crystalline  lens, 
which  is  about  one  third  of  an  inch  long  and  composed  of 
a  number  of  concentric  layers  like  the  coats  of  an  onion. 
The  lens  curves  out  both  in  front  and  behind ;  we  say  it 

is  double  convex.  The 
main  part  of  the  eyeball 
is  filled  with  the  vitreous 
(glassy]  humor,  that  looks 
like  the  white  of  an  egg 
and  serves  to  keep  the  deli- 
cate retina  in  position. 


FlG.  145.  —  Showing  changes  in  the 
lens  in  accommodation  (Zuppke). 


The  two  humors  and  the  crystalline  lens  bend  the 
rays  of  light  that  enter  the  pupil  of  the  eye  so  that 
they  are  brought  to  a  point  on  the  sensitive  retina. 
The  lens  is  important  in  focusing  the  light  because  it 


xvin  THE   SPECIAL   SENSES  AND   SENSATIONS  271 

is  suspended  in  a  ligament  which  holds  it  in  place  and 
changes  its  thickness  so  as  to  adjust  (accommodate)  the 
eye  for  objects  near  by  and  far  away. 

1.  Cut  through  the  cornea  of  the  sheep's  eye  and  you  will  find  a 
liquid  called  the  aqueous  humor. 

2.  Cut  away  the  iris  and  find  the  lens.     Notice  its  size,  shape, 
curvatures,  and  transparency.     Place  the  lens  on  print  and  notice 
the  result. 

3.  Cut  back  on  one  side  so  as  to  remove  the  vitreous  humor  that 
fills  the  back  part  of  the  eyeball. 

4.  Find  the  blind  spot,  or  the  place  where  the  optic  nerve  enters 
the  eyeball. 

5.  Near  the  blind  spot  is  a  very  slight  depression  at  the  center 
of  the  eyeball,  known  as  the  yellow  spot.     Find  it. 

187.    The  Course  of  Light.  —  The  rays  of  light  coming 
from  an  object  radiate  in  all  directions.     If  the  eye  is 


FlG.   146.  —  The  formation  of  an  image  on  the  retina.     (From  Huxley.) 

so  turned  as  to  receive  some  of  the  vibrations,  those 
which  fall  upon  the  pupil  enter  the  eye  and  pass 
through  the  aqueous  humor,  the  crystalline  lens,  and 
the  vitreous  humor.  The  muscles  of  the  capsule  of  the 
lens  so  change  its  curvature  as  to  bring  the  rays  to  a 
focus  on  the  retina.  There  is  now  an  image  of  the 
object  produced  on  the  retina,  and  this  image  excites 


272  HUMAN   PHYSIOLOGY  CHAP. 

the  delicate  nerve  endings.  The  impressions  are  carried 
over  the  optic  nerve  to  the  occipital  lobe  of  the  brain, 
where  they  are  interpreted.  The  vibrations  of  ether 
pass  through  the  conjunctiva,  the  cornea,  the  aqueous 
humor,  the  pupil,  the  lens,  the  vitreous  humor,  and 
then  are  received  on  the  retina. 

The  point  at  which  the  optic  nerve  enters  the  eye- 
ball is  not  sensitive  to  ether  vibration,  and,  for  that 
reason,  is  known  as  the  "  blind  spot"  To  find  the  blind 
spot,  close  the  left  eye,  focus  the  right  steadily  on  the 
triangle  below,  and  then  move  the  book  slowly  until  it 


FIG.  147.  — To  find  the  blind  spot. 

is  about  a  foot  from  the  eye,  when  the  large  outline  of 
the  blind  spot  on  the  right  will  disappear  entirely.  The 
point  of  clearest  vision,  located  at  the  centre  of  the  retina 
just  outside  of  the  blind  spot,  is  called  the  "  yelloiv  spot" 
188.  Defective  Vision.  —  The  lens,  which  is  so  impor- 
tant in  bringing  the  rays  of  light  to  a  focus  on  the  yel- 
low spot  of  the  retina,  may  be  defective.  Then  the  rays 
cannot  be  properly  focused.  The  lens  may  be  too  con- 
vex or  the  eyeball  too  long,  so  that  the  light  is  brought 
to  a  focus  before  reaching  the  retina  ;  this  is  called  "  near- 
sightedness."  The  book  must  be  held  very  close  to  the 
eyes  in  order  to  read  and  the  body  bent  over  in  writing. 


XVIII 


THE   SPECIAL   SENSES   AND   SENSATIONS 


273 


The  lens  may  be  too  nearly  flat  or  the  eyeball  too  short, 

so  that  the  rays  of  light  focus  behind  the  retina ;   this 

is  called  "farsightedness"  The 

book    must   be  held  far  from 

the  eyes  because  objects  near 

by  cannot  be  seen  well.     The 

cornea  may  not  curve  uniformly 

in   all   directions,   so   that   the 

rays  are  not  all  focused  on  the     FlG-  148.  -  Parallel  rays  focused 

on  the  retina  (Zuppke). 

same    surface ;    this   is   called 

astigmatism.     The   muscles  of  the  two   eyes  may  not 

work  as  they  should  in  focus- 
ing upon  near  and  far  ob- 
jects or  in  moving  the  two 
eyes  together. 

As  a  matter  of  fact,  very 
few  eyes  are  perfect  in 
every  respect.  But  most  of 
the  defects,  if  not  too  serious, 

are  overcome  by  the  wonderful  power  of  accommodation 

which  the  eyes  of  the  young 

possess.    As  long  as  a  person 

is  in  good  health  or  does  little 

reading  or  studying,  he  may 

not  know  that  his  eyes  are 

defective.      When,    however, 

general  health  fails,  or  much 

indoor  work   requiring   close 

application  of  the  eyes  is  attempted,  the  eye  strain  may 

be  so  severe  as  to  cause  serious  discomfort  and  lead  to 


FlG.  149.  —  Parallel  rays  focused  in 
front  of  the  retina  (Zuppke). 


FlG.  150.  —  Parallel  rays  focused 
behind  the  retina  (Zuppke) . 


274  HUMAN   PHYSIOLOGY  CHAP. 

dangerous  nervous  diseases.  These  defects  should  be 
corrected  by  using  spectacles  or  eye-glasses,  properly 
adjusted,  or  by  an  operation,  as  the  case  may  require. 

With  a  set  of  Snellen's  test-types,  make  an  examination  of  your 
own  eyes.  Test  for  nearsightedness,  farsightedness,  and  astigmatism. 

189.  Care  of  the  Eyes.  —  Although  the  eye  is  a  delicate 
and  sensitive  organ,  it  has  a  wonderful  power  of  accom- 
modation, and,  under  favorable  conditions,  can  do  an 
immense  amount  of  work.  That  is  why  the  eyes  are 
so  often  abused.  It  is  only  after  they  have  become 
diseased  and  cause  discomfort  that  they  are  given  any 
special  care  by  most  persons.  Let  us  'learn  a  few  of 
the  more  important  things  about  the  use  and  care  of 
healthy  eyes. 

1.  After  diseases,  like  measles,  diphtheria,  and  scar- 
let fever,  the  eyes  are  weak  and  should  not  be  used  for 
close  work  for  several  weeks.     At  such  times  it  is  an 
easy  matter  to  permanently  injure  the  eyes. 

2.  Do   not   overwork   the  eyes  by  reading,  writing, 
sewing,  or  doing  any  kind  of    close  work,  when   they 
smart  or  tingle.     When  the  eyes  are  tired  they  should 
have  rest. 

3.  Do  not  work  facing  a  strong  light.    It  should  come 
from  the  rear  and  over  the  left  shoulder  to    be   most 
comfortable. 

4.  All  close  work  should  be  done  during  the  daytime 
and  in  the  best  of   light.     The  twilight  of  the  early 
evening  has  ruined  many  good  eyes. 

5.  The  position  of  the  body  is  very  important  in  the 
proper  use  of   the  eyes.     You    should   not  read    lying 


xvin  THE   SPECIAL   SENSES   AND   SENSATIONS  275 

down,  or  with  the  head  bent  over,  as  when  working  at 
a  low  desk.  The  habit  of  reading  after  going  to  bed 
is  very  injurious. 

6.  Reading  on  trains,  on  street  cars,  in  carriages,  or 
while    walking    about   is    a  very  severe    strain    on    the 
muscles  of  accommodation,  and  should  be  avoided. 

7.  Books  and  papers  should  have  large,  clear  type 
that  is  well  leaded,  good  paper,  not  too  highly  sized, 
and  lines  not  to  exceed  four  inches  in  length.     Poor, 
cheap  books,  with  small,  blurred,  indistinct  type,  should 
be  avoided  if  possible. 

8.  The  head  should  always  be  held  erect  in  reading, 
with  the  book  or  paper  nearly  on  a  level  with  the  eyes 
and    about   fourteen    inches    away.      Many    habitually 
hold  their  work  too  close  to  the  eyes  and  in  that  way 
overtax  the  muscles  of  accommodation. 

9.  When  a  small  object  gets  into  the  eye  it  should 
be  carefully  removed.     Often  the  tears  will  wash  the 
object    toward    the    inner 

corner  of  the  eye,  where 
it  can  be  seen  and  easily 
taken  out.  If  necessary, 
the  lid  may  be  turned  in- 
side out,  as  shown  in  the 
figure,  and  the  object  re- 

moved.        Do    not    rub    the         FIG.  151.  — The  upper  lid  inverted 

(Zinns). 

eye. 

10.  The  blackboard,  slates,  paper,  and  pencils  used  in 
the  schools  should  be  of  the  best  quality  and  kept  in  good 
condition,  so  that  no  undue  eye  strain  may  result, 


276  HUMAN   PHYSIOLOGY  CHAP. 

11.  If  the  eyes  cause  discomfort,  headache,  or  a  dull 
feeling  about  the  head,  consult  an  oculist.     Never  have 
anything  to   do  with   the   quack  eye   doctors  or  street 
venders  of  spectacles. 

12.  Alcohol  congests    and  inflames  the   conjunctiva 
and  lids,   impairs   vision   in    acuteness    and   quickness, 
and    may    produce    changes   in    the    lens,    retina,    and 
optic  nerve. 

13.  Tobacco  smoke   irritates  the  delicate   lining  of 
the  eyes  and  blurs  the  vision. 

j 

SUMMARY   OF  THE   MAIN   POINTS 

1.  Every   sensory  nerve    brings   impressions  to   the  brain, 
from  which  we  gain  a  knowledge  of  our  own  bodies  and  of 
the  world  about  us.     These  impressions  we  call  sensations. 

2.  The  impressions  received  from  the  internal  organs  give 
us  sensations  of  hunger,  thirst,  faintness,  giddiness,  discomfort, 
fatigue,  itching,    burning,    aching,    shuddering,   creeping,    etc. 
These  are  called  general  sensations. 

3.  There  are  little  touch  corpuscles  in  the  papillae  of  the 
dermis  which  serve  as  end  organs  of  touch.    They  are  most  nu- 
merous on  the  tip  of  the  tongue  and  on  the  ends  of  the  fingers. 

4.  The  tongue,  soft  palate,  and  pharynx  are  supplied  with 
end  organs  of  taste  called  taste  buds.     They  give  us  sensations 
of  sweet,  spur,  bitter,  and  salt     Taste  guides  in  the  selection 
of  foods  and  gives  an  added  pleasure  to  eating. 

5.  The  mucous  membrane  in  the  upper  part  of  the  nose  is 
provided  with  nerve  endings  that  form  the  end  organs  of  smell. 

6.  The  ear  is  the  end  organ  of  hearing.     It  consists  of  the 
external,  middle,  and  internal  ear.     The  external  consists  of 
the  concha  and  auditory  canal ;  the  middle,  of  the  drumhead  or 
tympanum,  the  chain  of  three  bones  stretching  across  a  hollow 


THE   SPECIAL   SENSES   AND    SENSATIONS  277 

chamber,  and  the  F^ustachian  tube  ;  and  the  internal,  of  the  bony 
labyrinth  containing  the  membranous  labyrinth  which  is  sur- 
rounded by  the  perilymph,  and  which  contains  the  endolymph. 

7.  The  internal  ear  consists  of  three  parts :  the  vestibule, 
the  semicircular  canals,  and  the  cochlea.     The  auditory  nerve 
sends  fibers  to  all  these  parts. 

8.  Sound  waves  are  caught  by  the  concha  and  directed  in 
through  the  auditory  canal ;    they  beat  against  the  drumhead, 
causing  it  to  vibrate ;  this  imparts  its  motion  to  the  chain  of 
bones  which  intensify,  modify,  and  focus  the  vibrations  upon 
the  oval  window  ;  here  the  vibrating  membrane  communicates 
its  movement  to  the  liquids  of  the    ear  which  act  upon  the 
membranous  labyrinth ;  and  this  excites  the  ends  of  the  audi- 
tory nerves. 

9.  The  ear  is  a  very  delicate  and  complicated  organ  and 
should  receive  a  certain   amount  of  care  daily.     If  in    good 
health,  the  chief  caution  is  :   Keep  the  concha  clean  and  do  not 
meddle  with  the  auditory  canal. 

10.  The  eye  is  the  end  organ  of  sight.     The  eyeball  consists 
of  three  layers  :  the  sclerotic  coat  and  cornea,  the  choroid  and 
iris,  and   the   retina.     The   globe    is    filled  with    the    aqueous 
humor,  the  lens,  and  the  vitreous  humor.     The  cornea  is  trans- 
parent, and  the  iris  has   an   opening  at  its  center,  the  pupil, 
which  determines  the  amount  of  light  that  shall  enter. 

11.  The  eyeball  has  six  large  muscles  which  turn  it  in  all 
directions,  and  many  small  muscles  which  adjust  the  eye  for  far 
and  near  objects. 

12.  The    eye    is    protected  by  the  eyelids,  eyelashes,  eye- 
brows, lachrymal  glands,  tear  ducts,  and  by  the  orbit  itself. 

13.  The    rays   of  light   from   an  object    pass    through  the 
cornea,  the  aqueous  humor,  the  pupil  of  the  iris,  the  lens,  the 
vitreous   humor,   and   are   focused   on   the  yellow  spot  of  the 
retina.     The  impressions  are  then  carried  to  the  occipital  lobe 
of  the  brain  over  the  great  optic  nerve. 


278  HUMAN   PHYSIOLOGY  CHAP,  xvm 

14.  Farsight,  nearsight,  and  astigmatism  are  due  to  an  im- 
perfect eyeball  or  lens,  and   should  be  corrected   by  wearing 
properly  fitted  spectacles  or  eyeglasses. 

15.  The  eye  is  a  delicate  and  sensitive  organ  capable  of 
doing  an  immense  amount  of  work  under  favorable  conditions. 
Observe   the   cautions    mentioned   above,  and  use  your  good 
sense  in  all  work  requiring  the  use  of  the  eyes. 


CHAPTER   XIX 

BACTERIA   AND    DISEASES 

190.  Bacteria.  —  We  have  already  learned  something 
of  the  deadly  work  of  bacteria  and  other  microorgan- 
isms in  previous  chapters,  but  shall  now  study  them  a 
little  more  closely  to  learn  their  relation  to  us  in  health 
and  in  disease.  Bacteria  are  among  the  smallest  and 
simplest  forms  of  plant  life 
known  at  present.  They  are 
so  very  small  that  it  has 
been  difficult  to  study  them. 
But  now  many  scientists  are 
devoting  their  whole  time  to 
a  careful  investigation  of  mi- 
croorganisms with  the  best 
and  most  expensive  micro- 
scopes and  other  appliances  FIG.  152.— The  three  kinds  of 

,,  ,          1^-1  bacteria  (Pratt). 

that  can  be  obtained. 

The  largest  bacteria  are  only  a  few  hundred-thou- 
sandths of  an  inch  in  diameter.  They  are  either  spheri- 
cal, rod-shaped,  or  screw  like,  and  are  known  as  the 
cocctfSj  bacillus,  or  spirillum  respectively.  Any  of  these 
forms  may  occur  singly,  or  in  pairs,  and  some  of  them 
even  in  long  chains.  They  multiply  and  grow  so  rap- 

279 


280  HUMAN   PHYSIOLOGY  CHAP. 

idly  that  a  single  one  may  produce  over  sixteen  million 
in  twenty-four  hours,  under  favorable  conditions.  Like 
fine  dust  or  tiny  spores  they  are  carried  about  every- 
where by  the  wind  and  water.  Some  have  a  wonderful 
power  to  resist  heat,  cold,  and  moisture,  and  can  live 
under  influences  which  destroy  all  other  forms  of  life. 

Some  kinds  of  bacteria  are  the  causes  of  diseases 
among  the  lower  animals  and  in  man,  while  the  major- 
ity are  among  man's  most  useful  agencies  in  many 
ways.  We  shall  see  how  they  are  useful  to  man  and 
what  relation  they  have  to  diseases. 

191.  Bacteria  as  our  Friends.  —  Some  of  these  little 
organisms  are  very  useful  to  us.  All  decay  or  decom- 
position of  vegetable  and  animal  matter  is  due  to  the 
chemical  action  of  bacteria.  In  this  way  all  dead  or- 
ganic matter  is  broken  up  into  simpler  substances  that 
can  be  used  by  the  growing  plants.  They  serve  as 
scavengers  to  clean  up  all  dead  organic  wastes  and  at 
the  same  time  send  into  the  atmosphere  a  large  amount 
of  carbon  dioxid  which  growing  plants  can  use  for 
food.  The  amount  of  carbon  dioxid  exhaled  by  man 
and  the  lower  animals  is  not  sufficient  to  supply  the 
demands  of  the  vegetable  kingdom.  The  plants  retain 
only  the  carbon  and  exhale  the  oxygen  which  we  in 
turn  breathe.  The  bacteria  produce  important  commer- 
cial products,  as  many  organic  acids,  and  most  of  the 
saltpeter.  The  bacteria  in  the  soils  of  field  and  garden 
are  at  work  constantly  changing  and  decomposing  cer- 
tain materials  and  preparing  the  food  supply  for  the 
growing  crops.  The  leguminous  plants,  as  clovers, 


XIX 


BACTERIA  AND   DISEASES 


281 


peas,  beans,  lentils,  vetches,  lupines,  etc.,  have  the 
power  to  use  the  free  nitrogen  of  the  air  because  in  the 
little  knots,  balls,  or  tubercles  found 
in  their  roots  there  are  countless 
bacteria  living  as  parasites  and  pro- 
ducing important  nitrate  compounds 
which  the  plants  use  for  food.  No 
plant  can  grow  in  a  soil  that  does  not 
contain  nitrates  unless  it  can  produce 
them  by  the  aid  of  bacteria.  All 
leguminous  plants  are  important  as 
fertilizers  because,  when  they  decay, 
they  give  to  the  soil  nitrates  produced 
by  bacteria.  So  useful  are  these  tiny 
organisms  that  neither  plants  nor  ani- 
mals could  live  without  them. 

192.  Bacteria  as  Enemies. — The  temperature,  mois- 
ture, and  food  supply  in  certain  parts  of  the  human 
body  furnish  a  favorable  soil  for  some  kinds  of  bacteria. 
They  are  very  fond  of  albumins,  such  as  occur  in  the 
blood  and  lymph.  The  mouth,  throat,  and  intestines 
are  always  swarming  with  these  little  organisms,  where 
they  cause  decay  or  decomposition  of  foods,  or  attack 
the  blood  directly  when  the  capillaries  become  inflamed, 
as  in  colds. 

The  conditions  under  which  the  different  kinds  of 
bacteria  grow  vary  greatly.  The  vast  majority  cannot 
grow  in  the  human  body  at  all,  a  few  grow  nowhere  else, 
some  grow  only  in  certain  of  the  lower  animals,  others 
in  all  alike,  some  will  grow  only  in  a  single  organ  or 


FIG.  153.  —  Tubercles 
on  root  of  common 
bean  (Johnstone). 


282  HUMAN   PHYSIOLOGY  CHAP,  xix 

tissue  of  the  body,  others  almost  anywhere.  Many 
kinds  of  bacteria  are  entirely  harmless  when  taken  into 
the  body,  because  they  do  not  find  conditions  favorable 
for  rapid  multiplication.  We  think  that  all  bacteria 
would  produce  diseases  if  they  grew  as  fast  in  the  body 
as  they  can  under  favorable  conditions.  It  is  well 
known  that  bacteria  produce  poisonous  products  to 
which  .diseases  are  due.  There  are  then  two  important 
factors  to  consider :  first,  the  ability  to  multiply,  and 
second,  the  capacity  to  manufacture  poisons.  The  dis- 
ease germs  may  become  so  numerous  as  to  interfere, 
by  their  very  presence,  with  the  circulation,  and  cause 
diseases  in  any  part  of  the  body.  The  chief  danger 
comes  from  the  poisonous  products  formed  out  of  the 
body  substances  and  foods  and  given  to  the  blood  or 
tissue  cells.  Just  as  soon  as  a  sufficient  amount  of 
poison  has  been  absorbed  fever  is  produced. 

Consumption,  diphtheria,  pneumonia,  typhoid  fever, 
cholera,  lockjaw,  malaria,  grippe,  smallpox,  scarlet 
fever,  measles,  mumps,  whooping  cough,  meningitis, 
erysipelas,  scarlatina,  leprosy,  chicken  pox,  yellow  fever, 
relapsing  fever,  anthrax,  glanders,  and  dysentery  are 
among  the  communicable  diseases,  many  of  which  are 
known  to  be  due  to  these  little  germs. 

193.  How  Disease  Germs  get  into  the  Body.  —  If  we 
wish  to  war  against  the  disease  germs,  we  must  know 
where  they  come  from,  how  they  travel  from  one  place 
to  another,  and  how  they  get  into  the  body.  Many 
germs  can  live  in  the  body  of  the  host,  and  may  be 
transferred  to  another  person  by  actual  contact  as,  for 


Consumption. 


Diphtheria. 


Diphtheria. 


Pneumonia. 


Typhoid. 


Typhoid. 


Cholera.  Lockjaw.  Grippe. 

FIG.  154.—  Several  disease-producing  bacteria.     (Diagrammatic  by  Pratt.) 


284  HUMAN  PHYSIOLOGY  CHAP. 

example,  those  causing  smallpox,  measles,  scarlet  fever, 
and  other  eruptive  diseases  common  to  childhood. 
These  are  called  contagious  diseases.  Some  germs  can 
live  for  a  long  time  outside  of  the  body,  as  in  air,  water, 
and  foods.  These  are  more  dangerous  to  public  health 
because  they  can  be  carried  a  long  distance  and  attack 
a  whole  city  or  sweep  over  a  continent  almost  in  a 
day.  Diseases  of  this  kind  are  called  infectious.  Many 
diseases,  as  erysipelas,  diphtheria,  and  consumption, 
belong  to  both  classes. 

Disease  germs  enter  the  body  through  the  mouth  and 
nose  and  get  into  the  intestines  and  air  passages.  The 
germs  found  in  the  air,  as  those  of  diphtheria,  scarlet 
fever,  and  consumption,  get  into  the  lungs  through  the 
ordinary  processes  of  breathing.  Germs  contained  in 
water  and  foods  get  into  the  alimentary  canal  and  attack 
the  organs  of  digestion.  Those  of  typhoid  fever,  dysen- 
tery, and  cholera  belong  to  this  class.  These  germs 
cannot  travel  through  the  air.  The  only  way  to  guard 
against  such  diseases  is  to  eat  good,  well-cooked  foods 
and  drink  water  that  has  been  boiled.  Some  germs  gain 
entrance  through  wounds  or  cuts  in  the  skin.  The 
germs  of  lockjaw  always  enter  in  this  way,  and  those  of 
boils,  abscesses,  and  malarial  fevers  frequently  do.  In- 
sects are  important  agents  in  conveying  germs.  Recent 
investigations  show  very  conclusively  that  the  mos- 
quito injects  the  germs  of  malaria  and  yellow  fever 
into  the  blood,  and  hence  we  may  regard  the  mosquito 
as  the  most  important  agent  in  the  spread  of  these 
diseases. 


xix  BACTERIA  AND   DISEASES  285 

194.  Disease  Germs  in  the  Body.  —  It  is  impossible  to 
keep  out  of  the  way  of  the  many  disease  germs  that 
surround  us  at  all  times.  We  breathe,  eat,  drink,  and 
touch  these  little  organisms  every  day  and  so  cannot 
avoid  taking  them  into  our  bodies.  Why,  then,  are  we  not 
sick  oftener?  It  is  because  the  human  body  has  a 
wonderful  power  of  defense  against  germs  of  all  kinds 
as  long  as  it  is  kept  in  a  good  physical  condition.  It 
does  not  let  the  germs  grow  and  produce  disease  if  it 
can  possibly  help  it. 

If  the  body  has  the  power  to  resist  the  action  of 
bacteria,  we  say  it  is  immune  to  tJie  disease.  Natural 
immunity  is  due  to  a  high  degree  of  vitality  in  all  tissues 
and  cells  of  the  body  and  is  thought  to  be  inherited. 
Among  the  agencies  and  conditions  that  make  the  body 
subject  to  the  invasion  of  disease  germs  we  may  men- 
tion poor  or  insufficient  foods  and  impaired  digestion ; 
fatigue  and  exhaustion ;  exposure  to  cold,  filth,  and 
unhygienic  surroundings;  vicious  habits  and  drunken- 
ness ;  and,  in  fact,  everything  that  tends  to  disturb  the 
functions  of  any  organ  of  the  body.  On  the  other 
hand,  an  abundance  of  good,  wholesome  food  and  pure 
water,  an  adequate  supply  of  pure,  fresh  air,  a  sufficient 
amount  of  physical  and  mental  exercise  and  rest,  clean- 
liness, so*briety,  and  moderation,  and,  in  short,  a  life  well 
regulated  in  all  respects,  tend  to  fortify  the  body  against 
such  diseases. 

We  do  not  know  just  how  the  body  destroys  the  germs 
or  how  it  resists  the  action  of  the  poisons  which  they 
produce,  but  we  do  know  that  the  white  corpuscles  of 


286  HUMAN   PHYSIOLOGY  CHAP. 

the  blood  are  active  in  destroying  certain  bacteria,  that 
the  plasma  of  the  blood  and  lymph  can  kill  bacteria, 
and  that  the  serum  of  the  blood  may  contain  antitoxins 
which  poison  the  bacteria.  A  person  may  become 
immune  to  certain  diseases  by  vaccination,  protective 
inoculation,  and  other  methods  in  use  at  present.  In 
some  of  the  infectious  diseases  the  body  becomes  so 
changed  that  a  second  attack  seldom  occurs,  as  in  scar- 
let fever,  yellow  fever,  smallpox,  measles,  and  mumps ; 
while  in  others  the  immunity  lasts  only  for  a  short  time, 
as  in  diphtheria. 

If  the  body  cannot  successfully  resist  the  growth  of 
the  germs  or  the  poisons  they  produce,  it  must  yield  to 
the  attack  of  the  bacteria.  Most  of  the  diseases  due  to 
bacteria  are  commonly  known  as  fevers,  which  must 
run  a  certain  course.  Of  course,  fever  means  simply 
a  condition  of  the  body  in  which  there  is  a  rise  in  tem- 
perature, and  may  be  due  to  many  other  causes.  The 
course  of  those  due  to  germs  may  be  described  as 
follows :  — 

1.  Infection,  or  the  entrance  of  the  germs  into   the 
body. 

2.  Incubation,  or  the  period  of   growth  in  the  body 
without  any  bad  signs  of  their  presence. 

3.  Onset,  or  the  time  the  symptoms  of  disease  begin 
to  show  themselves. 

4.  Height,  or  the  time  the  fever  reaches  its  highest 
point. 

5.  Decline,  or  the  time  the  temperature  falls  to  the 
normal. 


xix  BACTERIA  AND   DISEASES  287 

6.  Convalescence,  or  the  time  it  takes  to  grow  strong 
and  well. 

We  shall  now  consider  more  in  detail  a  few  of  the 
common  communicable  diseases. 

195.  Consumption. — We  have  already  learned  that 
consumption  destroys  more  lives  in  this  country  than  any 
other  disease.  We  are  now  beginning  to  understand  the 
cause,  nature,  means  of  prevention, 
and  treatment  of  this  dreaded  dis- 
ease, and  we  may  hope  that  as  the 
general  public  becomes  more  intelli- 
gent on  this  subject  fewer  deaths 
will  be  caused  by  it.  Consumption 
can  be  taken  only  from  a  person 

rr  £  ,,          ,.  Tr    .,  FlG.  155.  —  Bacteria  of 

suffering  from  the  disease.      If  the  consumption, 

sputum  is  allowed  to  dry  on  the 
ground,  the  germs  get  into  the  air  and  must  be  inhaled 
with  the  air  we  breathe.  We  know  that  the  germs  of 
consumption  occur  in  meats  and  milk  from  diseased 
cattle  and  unless  destroyed  by  thorough  cooking  may 
get  into  the  body,  but  we  cannot  say  positively  that 
they  can  cause  consumption  in  man ;  most  scientists 
think  they  can.  There  are,  of  course,  many  other  ways 
in  which  persons  can  take  the  germs. 

When  healthy  persons  live  with  consumptives  great 
care  must  be  exercised,  for  it  is  easy  to  take  the  germs 
by  sleeping  in  the  same  bed,  using  the  same  eating  and 
drinking  utensils,  wiping  on  the  same  towel,  kissing  and 
caressing,  and  especially  by  carelessness  in  disposing  of 
the  sputum  and  excretions. 


288  HUMAN   PHYSIOLOGY  CHAP. 

If  the  inhaled  tubercle  bacilli  find  favorable  'condi- 
tions for  their  development,  they  multiply  rapidly,  causing 
inflammation  and  later  the  formation  of  tubercles  in 
different  parts  of  the  lungs.  Unless  the  disease  is 
checked  the  tissues  of  the  lungs  become  so  involved 
that  they  cannot  carry  on  their  functions  properly.  The 
bacteria  produce  poisons  which  tend  to  undermine  the 
health,  and  cause  a  loss  of  appetite  and  general  debility. 
The  disease  usually  begins  with  what  is  called  a  "  cold 
on  the  lungs "  and  a  cough.  From  the  very  first  all 
excretions  from  the  mouth  and  nose  contain  the  germs 
and  are  the  chief  source  of  danger. 

196.  Pneumonia.  —  A  specific  germ  is  the  cause  of 
pneumonia.  Pneumonia  occurs  both  in  hot  and  cold 
climates.  In  the  northern  part  of 
our  country  it  occurs  chiefly  in  late 
winter  and  early  spring.  The  germs 
are  inhaled  with  the  air  and  lodge  in 
the  air  passages  of  the  lungs,  where 
they  multiply  very  rapidly  if  condi- 
tions are  favorable.  Exposure  to  cold 
FIG.  156. -Bacteria of  and  moisture,  and  general  debility 

pneumonia. 

due  to  exhaustion,  alcoholism,  or  dis- 
eases of  certain  kinds,  precede  an  attack  of  pneumonia. 
All  such  conditions  tend  to  cause  congestion  and  inflam- 
mation in  the  lungs,  and  in  this  way  a  good  soil  is 
prepared  for  the  germs  of  this  dangerous  disease.  We 
know  that  the  excessive  use  of  alcoholic  beverages  may 
predispose  the  body  to  this  disease. 

A  person  is  not  likely  to  contract  pneumonia  if  he  eats 


Xix  BACTERIA  AND   DISEASES  289 

an  abundance  of  wholesome  foods  at  regular  hours  so  as 
to  maintain  the  nutrition  of  the  body  on  a  high  plane ; 
dresses  warm  and  dry,  so  as  to  guard  against  the  sudden 
changes  in  temperature ;  and  bathes  frequently,  so  as  to 
keep  the  skin  clean  and  the  pores  open. 

The  sputum  of  a  person  suffering  from  this  disease 
contains  the  living  germs ;  it  should  be  disinfected  at 
once.  All  articles,  as  clothing,  bed  linens,  etc.,  soiled 
with  the  sputum  should  be  thor- 
oughly scalded  as  soon  as  removed. 
Remember  that  if  the  sputum  is  al- 
lowed to  dry,  the  germs  which  it 
contains  get  into  the  atmosphere 
and  may  be  carried  abroad.  The 
death  rate  due  to  pneumonia  has 
increased  very  rapidly  since  1890.  FlG-  157- -  Bacteria  of 

cholera. 

197.  Cholera. — The  disease  known 

as  Asiatic  cholera  is  caused  by  a  little  comma  bacillus, 
which  sometimes  occurs  in  long  chains,  and  hence  is 
often  called  a  spirillum  or  a  spiral-shaped  bacterium. 
The  germs  are  taken  into  the  body  through  water  or 
food  that  has  become  contaminated.  Polluted  water  is 
probably  the  greatest  source  of  danger.  Flies  and  other 
insects  may  carry  the  germs  to  foods,  as  milk,  meats, 
and  fruits.  It  is  well  known  that  filth,  bad  foods,  im- 
pure air,  lack  of  proper  clothing  and  shelter,  all  favor 
the  spread  of  the  cholera  germ. 

The  disease  germs  attack  the  epithelial  cells  of  the 
mucous  membrane  of  the  intestines.  When  the  cells 
have  become  impaired  in  their  functions  or  destroyed, 


290  HUMAN   PHYSIOLOGY  CHAP. 

the  poisons  produced  are  absorbed  into  the  blood  and 
finally  paralyze  the  nerve  centers  controlling  circula- 
tion and  heat  production. 

198.  Typhoid   Fever.  —  This  disease  is  due  to  a  rod- 
shaped  bacillus.     The    germ   enters   the  body   through 

water,  milk,  or  other  foods.  The 
germ  is  contained  in  the  excretions 
of  patients,  which  are  its  only  source 
so  far  as  is  known  at  present.  The 
water  polluted  with  typhoid  germs 
used  in  the  dairy  or  in  washing 
vegetables  is  a  frequent  cause  of 
FIG.  158.  — Bacteria  of  this  disease.  Flies  and  other  insects 

typhoid  fever.  . 

spread  typhoid  germs. 

The  typhoid  germs  get  into  the  intestines  and  mul- 
tiply rapidly.  They  injure  the  walls  of  the  intestines, 
causing  ulcers,  and  *in  severe  cases,  hemorrhages  and 
perforations.  For  that  reason  the  patient  should  not 
be  given  any  solid  foods  at  all.  There  is  no  danger 
of  infection  except  from  the  excretions,  which  should 
be  properly  cared  for,  and  from  soiled  sheets  or  cloth- 
ing, which  should  be  carefully  disinfected  as  soon  as 
removed. 

199.  Dysentery.  —  This    is     an     infectious     disease, 
especially  common    among  children.     It   is    due  to  an 
organism  that  does   not  belong  to   the  bacteria.     The 
disease-producing  organism   probably   lives   in   the   soil 
and  water  and  gets  into  the  body  through  the  mouth 
with  water    and  foods.     The    organisms   develop   very 
rapidly  in  the  intestines  and  are  numerous  in  the  excre- 


xix  BACTERIA  AND   DISEASES  291 

tions  from  the  bowels,  which  should  be  carefully  disin- 
fected. When  dysentery  prevails,  all  drinking  water 
should  be  thoroughly  boiled,  and  no  uncooked  vegetables 
should  be  eaten. 

200.  Diphtheria.  —  This  disease  is  caused  by  a  rod- 
shaped  bacillus.  Diphtheria  belongs  to  the  class  of  in- 
fectious diseases,  but  is  probably  also  highly  contagious. 
The  germs  of  diphtheria  come  from  the  mouth  and 
throat  of  the  patient.  They  may  be  coughed  i  up  in 
bits  of  the  membrane  that  forms  in  the  throat,  and 
lodge  on  the  bedclothes,  furniture,  persons  near  by,  and 
on  the  walls  of  the  room.  The  germs  may  become 
completely  dry,  and  still  retain  life  and  be  able  to 
cause  the  disease  in  another  person.  Diphtheria  in 
the  house  of  the  dairyman  has  been  known  to  infect 
the  milk  and  cause  a  'general  outbreak  among  his 
patrons.  Cattle  probably  never  have 
the  disease,  but  cats  have  taken  it 
from  children  and  carried  it  else- 
where. 

The  germs  settle  in  the  throat  and 
soon  cause  a  yellowish  white  mem- 
brane to  form,  which  may  completely 
obstruct  the  air  passages.  The  dis-  FlG-  159. -Bacteria of 

diphtheria. 

ease  is  accompanied  by  sore  throat, 
a  croupy  cough,  and  a  choking  sensation.  Of  course 
not  every  case  of  sore  throat  is  diphtheria,  but,  if  at  all 
serious,  it  should  be  looked  upon  with  grave  suspicion. 
Diphtheria  is  one  of  the  diseases  that  is  being  success- 
fully treated  to-day  by  the  use  of  a  germicide  made  from 


292  HUMAN   PHYSIOLOGY  CHAP. 

the  serum  of  horses  that  have  been  inoculated  with  the 
disease  germs ;  it  is  called  diphtheria  antitoxin. 

201.  Scarlet  Fever.  —  This  disease  is  probably  caused 
by  a   germ,    although  as   yet  scientists  have  not  been 
able    to   find  out  the  real  -cause.     The  disease  is  con- 
tagious and  infectious  at  all  times,  but  especially  in  the 
later  stages,  when  the  epidermis  begins  to  peel  off  in 
fine   particles.     These    little    particles    may  be    carried 
from  one  person    to    another   in    various  ways  and  by 
numerous  agencies.     Scarlet  fever  at  the  house  of  the 
dairyman  has  been  known  to  infect  the  milk  and  cause 
the  disease. 

A  rash  or  skin  eruption  occurs  on  the  second  day, 
on  the  chest  and  thighs.  It  soon  spreads  to  all  parts 
of  the  body.  In  about  ten  days  the  skin  begins  to  peel 
off,  and  this  may  continue  from  one  to  five  weeks. 
This  is  the  time  of  greatest  danger,  and  the  patient 
should  be  kept  isolated  from  all  other  persons  during 
the  entire  time,  and  be  properly  cared  for,  because  a 
cold  is  sure  to  affect  the  kidneys  or  ears,  and  may 
leave  these  organs  permanently  weak,  or  even  result 
in  death. 

202.  Measles. — The  cause  of    measles  is  unknown, 
but  it  is  one  of  the  most  contagious  diseases  of  child- 
hood.    It  usually  begins  with  a  cold  in  the  head,  and 
on  the  fourth  day  an  eruption  of  the  skin  appears  on 
the  face,  which  later  spreads  to  all  parts  of  the  body. 
The   disease   is   most   contagious   in    the  early  stages, 
before  the  rash  appears,  and  for  that  reason  precaution 
cannot  be  taken  in  time  to  prevent  its  spread. 


xix  BACTERIA  AND   DISEASES  293 

Measles  often  brings  on  diseases  of  the  air  passages, 
as  bronchitis,  pneumonia,  and  consumption.  Death  is 
more  often  due  to  such  complications  than  to  the  dis- 
ease directly.  The  only  means  of  preventing  its  spread 
is  to  isolate  the  patient  during  the  entire  time  and  to 
disinfect  all  bedclothes,  dishes,  etc.,  used  in  the  sick 
room. 

German  measles  is  a  disease  quite  different  from 
either  measles  or  scarlatina,  but  the  skin  eruption 
resembles  both.  It  is  a  contagious  disease  whose  cause 
is  not  known.  It  is  much  milder  than  measles  and 
rarely  proves  fatal. 

203,  Smallpox.  —  Smallpox  is  an  infectious  and 
highly  contagious  disease  whose  cause  is  not  known,  but 
it  is  believed  to  be  due  to  bacteria.  On  the  third  day  an 
eruption  of  the  skin  appears  in  the  form  of  small  round 
lumps,  shotty  eruptions,  first  on  the  forehead  and  face, 
but  later  all  over  the  body.  In  these  lumps  a  clear 
fluid  is  found  in  the  early  stages,  later  a  yellow  pus,  and 
finally  a  scab  is  formed  about  the  twelfth  day.  The 
scabs  begin  to  fall  off  on  the  fourteenth  day,  and  in  the 
course  of  three  or  four  days  they  all  disappear,  usually 
leaving  pits  or  scars.  The  disease  is  very  contagious 
from  the  first  and  until  every  scab  has  fallen  off  and 
every  sore  has  fully  healed. 

The  disease  is  inhaled  from  the  air  and  probably 
never  taken  through  water  or  foods.  The  patient  should 
be  isolated,  and  all  articles  about  the  patient  and  the 
room  thoroughly  disinfected  or,  still  better,  burned.  No 
disease  can  be  more  easily  spread  abroad  than  smallpox. 


294  HUMAN   PHYSIOLOGY  CHAP. 

The  most  effective  means  of  preventing  and  eradicat- 
ing this  loathsome  disease  is  vaccination,  which  produces 
a  very  mild  form  of  the  disease  that  makes  the  person 
immune  for  a  number  of  years.  Vaccination  has  proved 
a  great  blessing  to  mankind,  for  it  has  saved  millions  of 
lives  from  this  deadly  scourge. 

Chicken  pox  is  a  mild,  "air-borne"  disease  in  which 
appear  skin  eruptions  that  sometimes  form  small  scabs. 
It  is  contagious  and  may  be  transmitted  until  the  scabs 
have  all  disappeared.  Small  scars  or  pits  are  sometimes 
left  that  disfigure  the  face. 

204.  Mumps.  —  This  is  a  very  contagious  disease  of 
childhood  and  youth,  in  which  the  salivary  gland  below 
the  ear  becomes  infected  and  very  much  enlarged.     It 
is  probably  caused  by  bacteria,  although    we    are   not 
certain  of  that.     Mumps  is  not  very  painful  and  seldom 
proves  fatal.     The  only  means  of   preventing  the  dis- 
ease is  complete  isolation  for  about  three  weeks. 

205.  Whooping  Cough. —  This  is  a  contagious  disease 
of  childhood.     It  is  accompanied  by  a  peculiar  spasmodic 
cough,  followed  by  a  whoop  (from  which  it  gets  its  name) 
as  the  breath  is  inhaled.     The  lungs  are  invaded  by  the 
germs  and  may  become  so  affected  as  to  cause  death. 
The  disease  may  be  communicated  from  one  person  to 
another  through  the  breath  and  matter  thrown  off  in 
coughing,  but  it   is    probably   not   carried   by   a   third 
person  nor  in  clothing.     It  is  contagious  from  the  first 
until  the  cough  and  whoop  have  entirely  ceased,  which 
usually  continue  for  a  period  of  from  three  to  six  weeks. 
During  this  time  the  patient  should  remain  isolated. 


xix  BACTERIA  AND   DISEASES  295 

206.  Malarial  Fever.  — This  class  of  fevers  is  due  to 
a  specific  organism  which  does  not  belong  to  the  class 
of    bacteria.     It    is  not   contagious.     Two  varieties   of 
malarial  fevers  are  known,  although   they   are  probably 
caused  by  the  same  organism.     These  fevers  generally 
occur  in    low,  marshy,  swampy    regions  and  are  most 
severe  near  marshes  that  are  periodically  flooded.     If 
the   swamps  are  properly  drained,  the  malarial   fevers 
soon  disappear. 

The  germs  probably  enter  the  body  through  the  water 
we  drink  and  the  air  we  breathe,  and  through  the  bites 
of  the  mosquito  and  other  insects.  These  fevers  may 
be  prevented  in  malarial  regions  by  draining  the  damp 
soils,  by  locating  residences  on  the  most  elevated  places, 
by  always  sleeping  indoors,  by  keeping  the  skin  free 
from  wounds  and  bites,  by  cooking  all  foods,  by  boiling 
the  drinking-water,  and  by  the  daily  use  of  quinine  in 
small  doses.  The  first  is  probably  the  most  effective 
means  of  stamping  out  malarial  troubles. 

207.  Yellow  Fever.  —  This    is    an   infectious   disease 
whose    cause    is    unknown.     It    occurs    chiefly   in  low, 
swampy,  tropical  countries,  but  epidemics  have  swept 
over  our  country  as  far  north  as  Philadelphia.     Many 
claim  that  the  poison  causing  yellow  fever  may  be  car- 
ried in  clothing,  in  papers  and  letters  through  the  mails, 
and  in  articles  of  merchandise  shipped  from  one  place  to 
another.     But  the  mosquito  is  doubtless  by  far  the  most 
important  agent  concerned  in  spreading  this  disease. 

The  introduction  and  spread  of  yellow  fever  may  be 
largely  prevented  by  maintaining  good  sanitary  condi- 


296  HUMAN   PHYSIOLOGY  CHAP. 

tions.  The  streets  should  be  clean  and  well  drained,  all 
garbage  and  excretions  from  patients  suffering  from  the 
disease  should  be  properly  disposed  of,  and  an  abun- 
dance of  clean,  wholesome  water  should  be  provided  for 
domestic  purposes.  All  yellow  fever  patients  should 
be  isolated  and  their  excretions  carefully  disinfected. 

208.  Grippe.  —  This  disease,  which  has  become  very 
common  of  late,  is  due  to  a  bacillus.     It  is  highly  con- 
tagious,   and    that    accounts    for   its 
rapid    spread    among    persons    col- 
lected in  large  numbers,  as  in  schools, 
factories,  and  shops.    The  germs  are 
probably  inhaled  and  then   develop 
rapidly  in  the  mucous  membrane  of 
the  air  passages.   The  common  symp- 

FIG.  !6o.- Bacteria  of       t()ms  ^Q   ffi  chm      headache    and 

grippe. 

violent  pains  in  the  spine.  Adults 
usually  suffer  much  more  than  children  from  an  attack 
of  grippe  or  influenza. 

If  every  case  could  be  reported  at  once  and  the  patient 
completely  isolated  until  fully  recovered,  the  spread  of 
this  disease  might  be  checked. 

209.  Pink  Eye.  —  This  is  a  disease    of   the  mucous 
membrane  lining  the  lids  and  covering  the  front  of  the 
eyeball.     It  is  caused  by  a  specific  disease  germ.     This 
disease  is  contagious  and  may  be  transmitted  by  any- 
thing that  comes  in  contact  with  the  matter  discharged 
from    a  diseased    eye.     The  hands  and  towels  are  the 
most  common  means  of  spreading  the  germs. 

The  eyes  become  red  and  inflamed  and  discharge  a 


xix  BACTERIA   AND   DISEASES  297 

watery  fluid  which  becomes  sticky  later,  so  that  the 
eyelids  may  be  firmly  gummed  together  every  morning. 
The  eyes  become  weak  and  highly  sensitive  to  ordinary 
light.  The  person  afflicted  should  be  isolated  until  he 
recovers. 

SUMMARY   OF  THE   MAIN    POINTS 

1.  Bacteria  are  very  small  microscopic  organisms  belonging 
to  the  vegetable  kingdom.     There  are  three  classes  as  to  shape, 

—  the  coccus,  the  bacillus,  and  the  spirillum. 

2.  Bacteria  multiply  very  rapidly,  and  some  kinds  can  resist 
cold,  moisture,  and  heat  so  successfully  that  they  can  live  under 
conditions  which  prove  fatal  to  all  other  forms  of  life. 

3.  Most  of  these  organisms  are  useful  to  man.     They  cause 
decay  or  decomposition  in  animal  and  vegetable  matter,  manu- 
facture a  large  amount  of  carbon  dioxid  for  the  use  of  plants, 
act  as  scavengers  to  clean  up  dead  matter  about  us,  form  certain 
commercial  products,  and  make  it  possible  for  some  plants  to 
obtain  nitrogen  directly  from  the  air. 

4.  Some  bacteria  can  grow  and  develop  best  in  the  human 
body  if  favorable  conditions  are  present. 

5.  Most  of  the  diseases  are  due  to  the  poisons  which  the 
bacteria  produce  in  the  body,  and  not  simply  to  the  presence 
of  the  organisms. 

6.  The  bacteria  get  into  the  body  through  the  air  passages, 
through  the  alimentary  canals  with  foods  and  water,  and  through 
bites  and  wounds  in  the  skin. 

7.  The  body,  if  in  good  health,  has  the  power  to  resist  the 
bacteria.      The   white  corpuscles    destroy  vast   numbers,   the 
plasma  of  the  blood  and  lymph  kills  many,  and  the  serum  of 
the  blood  may  contain  antitoxins  which  destroy  the  effects  of 
the  poisons  produced  by  the  germs. 

8.  If  the  tissues  and  organs  have  a  high  degree  of  vitality, 


298  HUMAN   PHYSIOLOGY  CHAP,  xix 

the  body  can  throw  off  the  disease  ;  but  if  not,  the  germs  soon 
gain  a  foothold,  and  fevers  are  the  inevitable  result. 

9.  If  the  body  will  not  take  a  certain  disease,  we  say  it  is 
immune  to  that  disease.  Natural  immunity  means  that  an  ani- 
mal cannot  take  a  disease  under  any  circumstances.  Artificial 
or  temporary  immunity  may  be  brought  about  by  antitoxins, 
by  vaccination,  or  by  an  attack  of  the  disease. 

10.  An  abundance  of  good  pure  foods  and  pure  water,  an 
adequate  supply  of  pure  fresh  air,  a  sufficient  amount  of  physi- 
cal and  mental  exercise  and  rest,  and  good  sanitary  surround- 
ings, tend  to  fortify  the  body  against  all  diseases. 

11.  Among  the  communicable  diseases,  many  of  which  are 
due  to  bacteria,  are  the  following :   consumption,  diphtheria, 
pneumonia,  typhoid   fever,   cholera,   lockjaw,   malaria,  grippe, 
smallpox,  scarlet  fever,  measles,  mumps,  whooping  cough,  cere- 
bro-spinal  meningitis,  erysipelas,  scarlatina,  leprosy,  chicken  pox, 
yellow  fever,  dysentery,  anthrax,  glanders,  and  relapsing  fever. 


CHAPTER   XX 

PUBLIC   HEALTH   AND   PERSONAL   HYGIENE 

210.  The  Problems.  —  In  cities,  towns,  and  in  rural 
districts  as  well,  the  health  and  well-being  of  each  per- 
son depend  to  a  large  extent  upon  the  general  sanitary 
conditions  of  the  entire  community.  This  fact  is  well 
understood  to-day.  Every  nation,  state,  and  city  makes 
provisions  through  laws  and  ordinances  for  the  pro- 
tection of  the  health  and  safety  of  its  people.  There 
is  not  a  single  city  or  town  which  does  not  have  its 
health  department,  boards,  committees,  inspectors,  and 
examiners. 

Some  persons  think  the  men  employed  in  a  large  city 
to  look  after  its  sanitary  and  hygienic  interests  have 
little  or  nothing  to  doexcept  when  some  dangerous  disease 
gains  a  foothold.  The  fact  is,  if  there  is  a  good  working 
sanitary  organization,  dangerous  diseases  never  occur, 
or  if  they  do,  they  are  soon  stamped  out.  What  does  it 
mean  to  keep  a  city  in  good  sanitary  condition  ?  We 
shall  get  some  idea  of  this  from  the  kind  and  number  of 
problems  that  come  to  its  sanitary  organizations.  Let 
us  see  what  some  of  these  problems  are. 

i.  To  inspect  all  foods,  as  meats,  vegetables,  and 
fruits,  shipped  into  the  city  and  offered  for  sale. 

299 


300  HUMAN   PHYSIOLOGY  CHAP. 

2.  To  inspect  the  milk  sold  in  the  city,  and  the  places 
where  it  is  produced. 

3.  To  examine  the  water  supply  and  warn  the  people 
when  dangerous  disease  germs  are  found  in  it. 

4.  To  examine  the  plumbing  and  sewerage  and  see 
that  they  are  kept  in  a  good  sanitary  condition. 

5.  To  keep  out  communicable  diseases  and  check 
their  spread  if  any  occur. 

6.  To  remove  and  dispose  of  the  garbage,   ashes, 
offal,  dead  animals,  and  refuse  of  all  kinds. 

7.  To  repair,  sweep,  clean,  sprinkle,  and  light  the 
streets  and  to  see  that  there  are    unobstructed  public 
thoroughfares. 

8.  To  inspect  all  public  schools,  public  baths,  lodging 
houses,  restaurants,  hospitals,  and  other  public  institu- 
tions and  see  that  they  are  kept  in  a  hygienic  condition. 

9.  To  control  all  public  nuisances  like  smoke,  offen- 
sive trades,  filth  on  shores,  public  dumps,  pond  holes 
and  swamps,  stables,  noises,  and  spitting  on  the  streets. 

10.  To  maintain  police  and  fire  departments  for  the 
safety  of  life  and  property. 

11.  To  keep  an   accurate  record  of  all  deaths  and 
births  that  occur  in  the  city. 

12.  To  investigate  and  answer  all  complaints  pertain- 
ing to  the  safety,  health,  and  comfort  of  its  citizens. 

All  these  and  numerous  other  matters  receive  atten- 
tion in  every  large  city.  The  departments  of  public 
health  and  general  sanitation  are  among  the  most  im- 
portant in  the  organization  of  any  densely  populated 
community. 


xx  PUBLIC   HEALTH   AND  PERSONAL   HYGIENE  301 

211.  Public  Intelligence.  —  While  every  city  and  town 
is  making  an  effort  to  maintain  good  sanitary  conditions 
through  its  officers  appointed  expressly  for  that  pur- 
pose, it  cannot  protect  the  public  as  it  should  without 
the    hearty    support    and    constant    cooperation   of   its 
citizens.     Not  only  should  they  see  that  their  officers 
perform  the  duties  assigned,  but  they  should  keep  them 
informed  as  to  dangerous  or  unsanitary  conditions  in  any 
portion  of  the  town  and  city. 

Every  good  citizen  should  be  informed  on  questions 
of  public  health,  should  know  the  dangers  of  unhygienic 
and  unsanitary  surroundings,  and  should  be  willing  to 
lend  his  support  to  all  movements  that  tend  to  protect 
the  health  and  safety  of  the  community.  Ignorant  per- 
sons are  often  unwilling  to  cooperate  with  the  organized 
efforts  for  better  sanitation,  and  for  that  reason  it  is 
almost  impossible  to  check  contagious  diseases  when 
they  occur  among  them.  When  all  people  become  in- 
telligent on  matters  pertaining  to  public  health  and 
general  sanitation,  and  live  up  to  their  knowledge,  com- 
municable diseases  will  be  unknown,  public  health  and 
safety  will  be  increased,  and  human  life  prolonged  by 
many  years.  The  hope  of  our  nation  lies  in  the  intelli- 
gence of  the  rising  generation. 

212.  Foods. — In  every  city  an  effort  is  made  to  in- 
spect all  food  products  offered  for  sale.     In  New  York 
there  are  about  four  hundred  experts  employed  by  the 
city  who  devote  their  entire  time  to  the  inspection  and 
examination  of  meats,  fish,  milk,  vegetables,  and  fruits. 
If  any  stale,  diseased,  impure,  or  otherwise  unwholesome 


302  HUMAN   PHYSIOLOGY  CHAP. 

foods  are  found,  they  are  destroyed  at  once.  Every 
state  and  nation  employs  expert  food  inspectors  to 
examine  all  imports  and  exports.  In  1899  our  gov- 
ernment inspected  53,087,994  slaughtered  animals,  of 
which  number  159,5 19  were  condemned  and  their  sale 
prohibited.  The  inspection  of  meats  and  other  slaugh- 
terhouse products  is  the  most  important  work  pertain- 
ing to  foods  that  our  government  attempts.  Usually 
the  states  deal  with  the  question  of  adulterations  and 
substitutions  of  foods,  and  the  federal  government  and 
local  authorities  pay  little  attention  to  it.  Massachu- 
setts spends  about  $10,000  annually  on  the  question 
of  adulteration  of  foods,  and  doubtless  this  amount  is 
saved  many  times  over  to  the  people  of  the  state. 

Pure,  wholesome,  unadulterated  foods  are  matters 
of  such  importance  to  the  health  and  well-being  of  any 
people  that  the  governments  are  maintaining  inspection 
and  experiment  stations  at  great  expense.  The  inspec- 
tion laws  should  be  strictly  enforced  in  the  rural  dis- 
tricts and  the  small  towns  and  villages,  as  well  as  in  the 
large  cities. 

213.  Water  Supply.  — To  supply  a  large  city  with  an 
abundance  of  pure  wholesome  water  for  drinking  pur- 
poses is  often  no  easy  task,  and  yet  no  one  thing  is 
more  essential  to  public  health.  The  chief  sources  of 
the  water  supplies  are  ponds  and  lakes,  storage  reser- 
voirs, rivers  and  streams,  and  deep  wells.  The  many 
shallow  wells  still  in  use  even  in  our  large  cities  are  the 
cause  every  year  of  hundreds  of  cases  of  typhoid  fever 
and  other  "  water-borne  "  diseases.  Sometimes  cities 


xx  PUBLIC    HEALTH   AND    PERSONAL   HYGIENE          303 

are  too  careless  in  disposing  of  the  sewage,  and  the 
source  of  the  supply  of  water  becomes  polluted  by  it. 
In  cities  situated  on  a  river  which  serves  as  a  sewer 
for  one  town  and  a  source  of  water  supply  for  others 
farther  down  the  stream,  it  often  happens  that  a  few 
cases  of  typhoid  fever,  or  other  "water-borne"  dis- 
eases, in  one  town  are  the  direct  cause  of  epidemics 

A/P/ 


FlG.  161.  —  Distribution  of  typhoid  fever  through  pollution  of  a  river.  In- 
tensity of  epidemic  shown  by  depth  of  shading.  No.  2  flows  into  No.  I ; 
A-G,  cities  situated  on  the  river;  a  water  intakes.  (Adapted  from  "  School 
Hygiene,"  issued  by  State  Superintendent  L.  D.  Harvey,  of  Wisconsin.) 

in   cities  located  below.      In   some  instances  a    single 
case  has  been  the  cause  of  an  epidemic. 

In  the  country,  outbuildings  and  barns  are  frequently 
so  situated  that  the  surface  waters  are  drained  into  a 
well  near  by.  Most  of  the  cases  of  "  water-borne  "  dis- 
eases occurring  in  the  rural  districts  are  due  to  polluted 
water  from  bad  wells. 


304  HUMAN   PHYSIOLOGY  CHAP. 

In  many  places  where  it'  is  difficult  to  obtain  pure, 
wholesome  water,  attempts  have  been  made  to  purify 
it  by  artificial  means.  For  the  past  fifty  years  filters 
have  been  used  very  extensively  in  Europe  to  purify  the 
water  for  cities.  We  are  now  introducing  them  in  this 
country.  The  safest  and  most  effective  way  to  purify 
water  for  private  use  is  to  boil  it  for  at  least  twenty 
minutes.  By  this  method  all  the  disease-producing  bac- 
teria are  killed,  and  the  water  becomes  innocent.  We 
cannot  be  too  careful  as  to  the  water  we  drink. 

214.  The  Air. — The  subject  of  pure,  fresh  air  has 
been  discussed  quite  fully  in  former  chapters.  The 
matter  of  wholesome,  odorless  air  is  of  great  importance 
to  our  comfort  and  health.  In  low,  damp,  swampy 
localities  the  air  always  contains  dangerous  bacteria. 
Doubtless  many  diseases  are  due  to  damp,  poorly  ven- 
tilated basements.  Cellars  are  especially  dangerous  if 
there  are  no  cement  floors  to  exclude  the  gases  that 
may  come  from  the  ground  beneath.  Dead  animals, 
waste  matter,  and  excretions  from  the  body  must  not  be 
allowed  to  pollute  the  air  we  breathe ;  they  should  be 
promptly  disposed  of  in  the  country  as  well  as  in  the 
city.  Of  course  not  all  bad  odors  are  dangerous, 
neither  is  all  odorless  air  safe  to  inhale. 

In  cities  it  is  often  quite  impossible  to  get  an  abun- 
dance of  pure,  odorless  air.  The  many  factories  and 
trades  keep  the  air  filled  with  odors  of  all  kinds.  While 
most  of  these  are  harmless,  they  are  not  agreeable,  and 
our  cities  are  doing  a  great  deal  to  control  all  such 
nuisances.  The  plumbing  must  be  inspected  frequently, 


xx  PUBLIC   HEALTH  AND   PERSONAL  HYGIENE  305 

all  garbage  promptly  removed,  the  filth  of  the  streets 
kept  from  accumulating,  the  stables  carefully  cleaned 
and  disinfected,  and  all  other  sources  of  offensive  and 
dangerous  air  should  receive  the  immediate  attention  of 
the  sanitary  organization. 

215.  Garbage.  —  One  of  the  most  important  problems 
for  every  city  is  the  disposal  of  its  garbage,  sewage, 
and  other  refuse.  How  shall  the  wastes  and  offal  of  all 
kinds,  from  private  houses,  hotels,  restaurants,  stores, 
markets,  produce  commission  houses,  and  the  like  be 
collected  and  disposed  of  ?  The  garbage  should  be  put 
into  a  tightly  covered  can  or  pail  for  that  purpose.  It 
is  then  collected  by  the  city  at  short  intervals,  from  one 
to  seven  times  a  week,  and  disposed  of  in  some  way. 
The  cans  or  pails  should  be  kept  where  they  will  not  be 
offensive,  and  occasionally  they  should  be  carefully 
washed  or  disinfected. 

The  garbage  is  usually  collected  at  public  expense. 
New  York  City  paid  about  $1,700,000  in  1900  for  col- 
lecting and  disposing  of  its  garbage,  and  over  fifteen 
hundred  persons  were  employed  to  do  the  work.  Boston 
employed  about  one  third  as  many  men  and  paid  about 
one  third  as  much. 

In  the  country  it  is  an  easy  matter  to  dispose  of  the 
garbage  in  some  way.  It  may  be  used  as  a  fertilizer, 
buried  in  the  ground,  fed  to  animals,  or  burned  in  a  stove. 
But  in  the  city  it  cannot  be  burned  without  producing 
odors  that  are  offensive  to  the  public,  and  the  first  two 
methods  cannot  be  employed  at  all  for  private  disposal. 
For  that  reason  the  city  itself  must  find  some  way  for 
x 


306  HUMAN   PHYSIOLOGY  CHAR 

getting  rid  of  the  wastes.     Various  methods  are  now 
used. 

Dumping  garbage  on  vacant  low  grounds  where  it 
may  serve  to  fill  up  low  places  is  the  simplest  method, 
but  this  cannot  be  used  except  by  some  of  the  smaller 
cities.  Such  dumps  are  nearly  always  dangerous  pub- 
lic nuisances.  Dumping  it  in  water  is  another  method, 
but  this  cannot  be  safely  used  in  most  cities.  It  is  usu- 
ally worse  than  dumping  on  the  ground,  because  the 
wastes  pollute  the  water  and  become  a  nuisance  for 
neighboring  cities.  Plowing  it  under  as  a  fertilizer  is 
being  abandoned  by  most  of  the  cities  which  tried 
this  method,  because  it  is  a  great  nuisance  and  costs 
too  much.  Feeding  it  to  animals,  as  swine,  sheep, 
poultry,  is  a  method  employed  by  many  of  the 
smaller  cities.  There  is  a  growing  feeling  against  this 
method.  At  present  the  hog  is  the  only  animal  to 
which  garbage  is  fed  extensively.  This  should  be  dis- 
continued, for  the  pork  is  of  an  inferior  quality  and  is 
more  likely  to  contain  trichinae.  In  many  cities  gar- 
bage is  sold  for  fertilizing  purposes  or  for  feeding  ani- 
mals. In  1898  the  city  of  Boston  received  over  $10,000 
from  this  source.  Reduction  processes  are  used  in  some 
of  our  large  cities  as  a  means  of  using  the  valuable  oils 
and  grease  the  garbage  always  contains.  These  pro- 
cesses are  not  yet  perfected,  so  that  the  returns  are  not 
very  large.  Cremation  or  burning  is  the  method  used 
in  Europe,  and  is  being  used  more  and  more  in  this 
country.  This  is  doubtless  the  most  satisfactory  method 
from  a  sanitary  point  of  view,  but  it  is  quite  expensive. 


xx  PUBLIC   HEALTH   AND   PERSONAL   HYGIENE  307 

Many  kinds  of  furnaces  have  been  invented  for  the 
purpose  of  burning  garbage. 

None  of  these  methods  seems  to  be  entirely  satisfac- 
tory, but  it  is  hoped  that  the  time  will  soon  come  when 
every  city  in  the  land  will  dispose  of  its  garbage  in  a 
sanitary  and,  at  the  same  time,  economical  way. 

216.  Cleanliness.  —  The  one  important  condition  of 
public  health  is  cleanliness.  Health  demands  not  only 
clean  air,  clean,  pure  water,  clean,  wholesome,  unadul- 
terated foods,  but,  in  addition  to  these,  clean  streets  and 
alleys,  clean  public  buildings  and  parks,  clean  private 
residences  and  yards,  and  cleanliness  of  person  and 
clothing. 

The  streets  must  be  cleaned,  sprinkled,  and  lighted 
in  order  to  keep  them  in  good  sanitary  condition. 
Every  city  employs  men  to  sweep  the  streets  and  re- 
move the  rubbish  that  collects  on  them  from  time  to 
time.  The  city  of  New  York  paid  over  $8,000,000  in 
1900  to  sweep,  clean,  and  light  its  streets,  and  employed 
about  thirty-six  hundred  men  to  do  this  work.  Boston 
paid  about  one  fourth  that  sum  for  a  similar  purpose. 

The  health  departments  make  a  careful  inspection  of 
all  private  yards,  barns,  and  residences,  and  see  that 
they  are  kept  in  a  clean  and  wholesome  condition  all 
the  time.  In  this  matter  public  intelligence  can  do 
much  to  maintain  good  sanitary  surroundings.  We 
must  remember  that  disease  germs  and  filth  of  all  kinds 
are  closely  associated,  and  therefore  the  only  way  to 
ward  off  diseases  is  to  insist  upon  cleanliness  in  all 
respects. 


308  HUMAN   PHYSIOLOGY  CHAP. 

Public  bathing  and  washing  conveniences  are  provided 
in  many  cities.  They  should  be  kept  clean  and  whole- 
some, for  if  they  are  not  in  good  hygienic  condition, 
they  may  be  the  means  for  spreading  diseases.  All 
who  are  careless  or  indifferent  about  the  cleanliness  of 
their  person  or  clothing  should  be  compelled  to  patron- 
ize such  public  necessities.  No  one  has  a  right  to 
endanger  the  life  and  health  of  those  with  whom  he 
may  come  in  contact,  because  of  personal  indifference 
to  sanitary  laws,  or  ignorance  of  them. 

217.  Diseases. — One  of  the  great  problems  that  the 
health  officers  have  to  deal  with  is  that  of  communicable 
diseases.  A  city  must  prevent  the  importation  of  com- 
municable diseases  as  far  as  possible.  Of  course  quar- 
antine can  be  successfully  used  only  at  seaports,  except 
in  a  very  few  diseases.  The  health  authorities  should, 
however,  attempt  to  keep  the  sanitary  conditions  excel- 
lent, so  that  the  city  as  a  whole  may  be  immune.  Each 
individual  must  do  his  part  to  keep  himself  and  his 
premises  in  a  good  sanitary  condition.  If  it  were  pos- 
sible for  the  health  officers  to  have  the  intelligent 
cooperation  of  every  citizen  within  their  jurisdiction, 
cities  might  become  immune  to  most  of  the  communica- 
ble diseases. 

Diseases  should  be  reported  to  the  health  officers 
immediately,  so  that  means  may  be  taken  to  prevent 
their  spread.  This  is  such  an  important  matter  that 
most  of  the  states  give  the  state  board  of  health  full 
authority  to  make  all  needful  regulations  relating  to 
communicable  diseases.  Usually  the  physician  and  the 


xx  PUBLIC   HEALTH   AND   PERSONAL   HYGIENE          309 

head  of  the  family  are  held  responsible  for  reporting  the 
diseases.  In  many  states  the  school-teacher  is  asked  to 
report  every  case  occurring  in  his  school  or  district. 

Laws  in  the  different  states  and  cities  are  not  uniform 
as  to  the  diseases  that  shall  be  reported.  The  following 
are  mentioned  by  most  of  them  :  smallpox,  cholera,  scar- 
let fever,  diphtheria,  croup,  yellow  fever,  typhus  fever, 
typhoid  fever,  measles,  whooping  cough,  consumption, 
meningitis,  and  leprosy.  A  few  cities  require  reports  on 
chicken  pox,  erysipelas,  mumps,  relapsing  fever,  dysen- 
tery, trichinosis,  plague,  pneumonia,  glanders,  and 
malaria.  The  fines  for  failure  to  report  communicable 
diseases  range  from  twenty-five  to  one  thousand  dollars. 

After  the  case  is  reported  the  posting  of  placards  is 
required  in  most  cities  to  indicate  the  fact  that  there  is 
danger  and  the  public  should  take  warning.  For  the 
more  dangerous  diseases  the  patient  should  be  isolated 
from  the  other  members  of  the  family  or,  still  better, 
taken  to  a  hospital  until  he  recovers.  If  the  patient  is  not 
taken  to  a  hospital,  all  children  and  persons  who  come 
in  contact  with  children  should  be  kept  indoors.  Every 
city  takes  great  pains  to  control  these  diseases  so  that 
they  shall  not  spread.  As  soon  as  a  case  is  reported  and 
precautions  taken  to  prevent  the  spread  of  the  disease, 
the  health  officers  should  make  a  thorough  investigation 
of  the  surroundings  to  ascertain  the  cause.  A  warning 
to  the  public  as  to  the  source  of  the  danger  is  often  the 
only  means  of  checking  the  progress  of  a  disease. 

218.  Schools  and  Diseases.  —  The  health  officers  and 
teachers  should  suspend  from  school  all  children  who 


310  HUMAN  PHYSIOLOGY  CHAP. 

have  been  exposed  to  any  of  the  dangerous  communica- 
ble diseases.  The  pupil  who  was  sick  and  all  other 
children  living  in  the  same  house  should  not  attend 
school  until  the  placard  has  been  removed  and  the 
house  disinfected  by  the  health  authorities.  It  is  best 
to  require  a  certificate  from  the  proper  authorities  before 
the  pupils  are  permitted  to  return. 

If  a  child  sick  with  a  dangerous  contagious  disease 
attends  school  even  for  a  part  of  a  day,  the  school 
should  be  closed  and  the  room  thoroughly  disinfected. 
Whenever  a  contagious  disease  is  likely  to  gain  a  strong 
foothold  in  a  community,  it  is  best  to  close  the  school 
entirely  to  keep  the  disease  from  spreading.  The  spread 
of  so  many  communicable  diseases  can  be  traced  directly 
to  the  schools,  that  parents  and  teachers  should  exercise 
the  utmost  vigilance  to  forestall  epidemics. 

219.  Disinfection.  —  The  process  of  killing  disease 
germs  and  spores  by  physical  means  or  by  chemical 
agents  is  known  as  disinfection.  We  have  already 
learned  that  adequate  ventilation  and  abundant  sunlight 
are  important  means  of  checking  the  growth  of  disease- 
producing  organisms.  When  disease  germs  are  present 
in  large  numbers,  more  radical  measures  must  be 
employed  to  destroy  them.  We  have  learned  that  the 
excretions  of  patients  suffering  from  some  of  the  com- 
municable diseases,  as  well  as  the  sick  rooms,  clothing, 
bed  linen,  furniture,  etc.,  may  contain  vast  numbers  of 
disease  germs,  which,  if  not  destroyed,  are  sources  of 
danger  to  the  public. 

The    chief    agencies   used    in    disinfecting    are   heat.. 


XX  PUBLIC  HEALTH   AND   PERSONAL   HYGIENE  311 

strong  chemical  solutions,  and  fumigation.  Clothing, 
bed  linen,  and  other  things  that  can  be  washed  may  be 
thoroughly  disinfected  by  boiling  or  steaming.  Articles 
that  cannot  be  submitted  to  such  a  treatment,  and 
excretions  and  drains,  may  be  disinfected  by  using  car- 
bolic acid  or  corrosive  sublimate.  These  are  both  very 
dangerous  poisons,  and  the  utmost  care  should  be  exer- 
cised in  their  use.  Neither  should  be  used  in  the  pure 
state,  but  must  be  diluted  with  water.  One  part  of  car- 
bolic acid  in  from  twenty  to  thirty  parts  of  water  makes 
a  very  good  general  disinfectant.  One  part  of  corrosive 
sublimate  (bichloride  of  mercury)  in  from  one  thousand 
to  six  thousand  parts  of  water  makes  an  excellent  disin- 
fectant for  use  in  scrubbing  woodwork,  furniture,  floors, 
and  walls,  and  it  is  often  employed  for  soiled  clothing 
and  excretions  from  the  body.  Many  other  chemicals 
are  used  as  disinfectants.  After  smallpox,  diphtheria, 
scarlet  fever,  and  other  highly  communicable  diseases 
have  been  in  a  house,  it  should  be  thoroughly  fumigated. 
For  this  purpose  formaldehyde  is  used  almost  entirely  at 
present,  for  it  seems  to  be  more  satisfactory  than  any 
other  substance.  The  physician  in  charge,  or  the  health 
department,  should  take  charge  of  the  -fumigation  and 
see  that  it  is  effectively  done. 

220.  Personal  Hygiene.  — The  health,  happiness,  and 
well-being  of  a  person  depend  upon  his  sanitary  sur- 
roundings and  personal  habits  of  living.  Both  require 
the  careful  attention  of  every  individual.  Public  health 
and  general  sanitation  are  indispensable  conditions  to 
individual  health,  and,  on  the  other  hand,  healthy  indi- 


3i2  HUMAN   PHYSIOLOGY  CHAP. 

viduals  must  make  up  a  healthy  community.  Every 
case  of  sickness  diminishes  the  public  health  and  en- 
dangers the  entire  community.  Lack  of  general  sanita- 
tion in  any  community  threatens  the  health  of  every 
individual. 

Under  favorable  sanitary  surroundings  the  death  rate 
is  decreased  and  the  span  of  human  life  lengthened, 
while  in  a  community  in  which  the  persons  are  ignorant 
and  careless  as  to  their  habits  of  living,  the  death  rate 
is  increased  and  the  period  of  life  shortened.  In  the 
United  States  the  length  of  life  (the  average  age  at 
death)  has  increased  about  four  years  during  the  dec- 
ade from  1890  to  1900,  as  shown  by  the  census  rate  of 
1900. 

It  is  a  hopeful  sign  that  the  death  rate  in  our  cities 
and  the  rural  districts  is  watched  carefully  from  year  to 
year,  and  it  should  be  a  matter  of  public  pride  to  see  it 
decrease  gradually.  Public  sanitation  will  not  accom- 
plish it  alone,  though  it  will  contribute  its  share,  but 
there  must  go  with  it  more  hygienic  personal  modes  of 
living.  The  important  thing  is  for  each  individual  to 
form,  early  in  life,  good  hygienic  habits  of  living,  and  to 
become  informed  on  all  matters  pertaining  to  public 
health  and  sanitation. 

SUMMARY   OF  THE   MAIN  POINTS 

1.  There  are  many  problems  of  public  health  and  general 
sanitation  that  should  receive  the  attention  of  the  intelligent 
citizens  in  every  community. 

2.  Many  of  the  problems  are  assigned  to  officers,  boards, 


xx  PUBLIC   HEALTH   AND    PERSONAL   HYGIENE  313 

and  committees   appointed   for  the   purpose  of  looking  after 
the  public  health. 

3.  All  such   organized  efforts    should  receive  the  support 
and   cooperation    of   every    intelligent    citizen.       The    health 
departments  cannot  do  what  they  should  without  the  aid  of 
the  public. 

4.  The  federal  government    and  each   state  and  city  ap- 
point persons  to  inspect   and   examine  foods,  as  meats,  fish, 
milk,  vegetables,  and  fruits.     These  inspectors  condemn  and 
destroy  whatever  they  find  that  is  stale,  adulterated,  or  other- 
wise unwholesome. 

5.  The  water  is  frequently    polluted    with    disease   germs, 
and  then  it  must  be  boiled  before  it  is  safe  to  use  for  drinking 
purposes.      Most   of  the   outbreaks  of  typhoid   fever  can  be 
traced  to  contaminated  water  or  milk. 

6.  Pure,  wholesome,  odorless  air  is  a  matter  of  great  im- 
portance to  the  health  of  any  people.     Much  can  be  done  in 
the  cities  to  control  the  nuisances  that  vitiate  the  atmosphere. 

7.  The  removal  and  disposal  of  the  garbage,  ashes,  rubbish, 
and  wastes  of  all  kinds  are  of  great  importance  to  good  sanita- 
tion. 

8.  The  chief  methods  of  disposing  of  the  garbage  in  the 
large  cities    are  dumping   on    low  grounds  and  in  the  water, 
plowing  under  as  a  fertilizer,  feeding'  to  swine  and  other  ani- 
mals, selling  to  farmers,  cremation,  reducing  to  certain  useful 
products,  as  fats  and  oils ;  but  cremation  is  the  most  satisfac- 
tory from  a  sanitary  standpoint. 

9.  The    air,    water,    foods,  houses,  cellars,  yards,   streets, 
alleys,  parks,  public  buildings,  public  baths,  persons,  and  cloth- 
ing should  all  be  kept  just  as  clean  as  possible  if  we  wish  to 
maintain  good  sanitary  conditions. 

10.  Every  communicable  disease  should  be  reported  at 
once  to  the  proper  authorities  by  the  attending  physician,  head 
of  the  family,  or  teacher  in  the  school, 


314  HUMAN   PHYSIOLOGY  CHAP,  xx 

11.  The  premises  should  then  be  carefully  inspected  to  as- 
certain the  cause  of  the  disease.     Placards  should  be  put  up 
to  warn  the  public  of  the  danger  within. 

12.  The  diseases  that  must  be  reported  in  most  places  are 
smallpox,  cholera,  scarlet  fever,  diphtheria,  croup,  yellow  fever, 
typhus  fever,  typhoid  fever,  measles,  whooping  cough,  consump- 
tion,  meningitis,  and  leprosy.     Some   add  chicken  pox,  ery- 
sipelas, mumps,  relapsing  fever,  dysentery,  trichinosis,  plague, 
pneumonia,  glanders,  and  malaria. 

13.  Fines  imposed  for  failure  to  report  communicable  dis- 
eases range  from  $25  to  $1000  in  different  states  and  cities. 

14.  All  school  children  exposed  to  communicable  diseases 
should  be  suspended  from  school  at  once.     If  the  contagious 
disease  is  likely  to  gain  a  foothold  in  the  community,  school 
should  be  closed  entirely  until  the  danger  is  past. 

15.  Personal    health  depends  to   a  large  extent  upon  the 
general  sanitary  surroundings,  and  public  health  in  turn  is  con- 
ditioned on  personal  habits  and  modes  of  living.     There  is  a 
close  relation  between  public  health  and  personal  health. 

1 6.  Every  individual  should  form  good  hygienic  habits  of 
living,  and  become  informed  on  all  matters  pertaining  to  pub- 
lic health  and  general  sanitation. 


CHAPTER   XXI 

FIRST   AID   IN   ACCIDENTS    AND    EMERGENCIES 

221.  Introduction.  —  When  we  are  very  sick  or  seri- 
ously injured,  we  want  to  be  treated  by  a  skilled  physician 
because  his  careful  study  and  long  experience  have  given 
him  a  deep  insight  into  all  matters  pertaining  to  the  wel- 
fare  of  our  bodies.     There  are,  however,  many  slight 
indispositions  and  injuries  whose  treatment  is  so  simple 
that  there  is  no  need  of  calling  a  physician.     In  severe 
illness  and  injuries  it  is  usually  very  important  for  the 
saving  of  life,  or  at  least  for  the  relief  of  suffering,  to  do 
something  at  once,  and  not  to  wait  until  the  physician 
arrives.     Be  certain,  however,  that  you  know  what  to  do 
and  how  to  set  about  it  before  you  offer  your  services. 

In  this  chapter  we  shall  learn  some  very  simple 
modes  of  treating  a  few  of  the  more  common  illnesses 
and  injuries  that  do  not  require  the  physician,  or  that 
demand  attention  in  case  no  physician  can  be  called 
immediately.  These  brief  suggestions  should  be  re- 
membered by  all. 

222.  Burns  and  Scalds.  —  If  the  burn  is  not  severe, 
apply   cold  water  at  first.       A  tablespoonful  of  baking 
soda  to  a  tumbler  of  water  makes  an  excellent  solution 
for  burns  of  all  kinds.     Equal  parts  of  linseed  oil  and 

315 


316  HUMAN  PHYSIOLOGY  CHAP. 

limewater  makes  an  excellent  liniment  for  dressing 
burns.  After  the  pain  has  disappeared  vaseline  should 
be  freely  used  until  the  wound  is  healed.  In  severe 
cases  call  a  skillful  physician  as  soon  as  possible. 

If  the  clothing  catches  fire,  it  is  best  to  lie  down  on 
the  ground  or  floor  immediately,  and  roll  back  and  forth 
until  the  flames  are  extinguished.  Wrap  up  in  a  rug, 
carpet,  blanket,  shawl,  overcoat,  etc.,  as  that  will 
smother  the  flames  at  once.  Do  not  run  outdoors,  for 
that  serves  to  fan  the  flames. 

223.  Sunstroke.  —  When  a  person  is  overcome  by  the 
heat,  he  should  lie  down  quietly  in  a  cool,  shady,  airy 
place.      Sponge    the    face,  neck,  and    hands  with  cold 
water.     Cloths  dipped  in  ice  water,  or,  still  better,  the 
ice  bag,  should  be  applied  to  the  head,  face,  neck,  and 
back.     In  severe  cases  the  clothing  may  be  removed 
and  the  patient  packed  in  ice  for  an  hour  or  more,  as 
may  be  necessary.     In  heat  exhaustion  the  body  is  cold 
and  moist  instead  of  hot  and  dry,  and  no  cold  should  be 
applied.     In   such   cases    hot   drinks    should   be  given 
freely  and    heat   applied    to    the   entire  body  so  as    to 
restore  the  normal  temperature  as  soon  as  possible. 

224.  Fainting,  —  Poor  ventilation,  disagreeable  odors, 
or  some  sudden  emotion  may  so  disturb  the  circulation 
of  the  blood  that  the  person  loses  consciousness.     Faint- 
ing is  not  generally  a  very  dangerous  matter,  and  very 
little  treatment  is  necessary.     Lay  the  person  flat  on  his 
back  with  the  hips  slightly  elevated.     If  there  is  vom- 
iting the  person  should  be  placed  on  his  side.     Loosen 
all   tight  clothing  about  the   neck  and   waist  at  once. 


xxi        FIRST  AID    IN  ACCIDENTS   AND   EMERGENCIES        317 

Place  the  person  near  an  open  window,  or,  still  better, 
carry  him  out  doors  so  that  he  may  have  plenty  of  fresh 
air.  If  necessary,  sprinkle  a  little  cold  water  on  the 
face  and  apply  ammonia  (smelling  salts)  to  the  nose. 
If  these  simple  remedies  do  not  restore  consciousness 
in  a  short  time,  send  for  a  physician. 

225.    Suffocation.  —  Among    the    common    causes    of 
suffocation  are  foul  gases,  as  from  old  wells  or  mines, 


FlG.  162.  —  Artificial  respiration  (Zuppke).    The  upper,  inspiration;  the  lower 

expiration. 

coal  gas  from  the  furnace,  stove,  or  range,  illuminating 
gas  from  a  jet  that  has  not  been  properly  turned  off, 
and  charcoal  fumes.  Carry  the  person  to  an  open 
window  where  he  may  have  plenty  of  fresh  air.  Loosen 
all  tight  clothing  about  the  neck,  chest,  and  waist.  Dash 
a  little  cold  water  in  the  face.  When  he  begins  to 
breathe,  hot  water  containing  a  little  ammonia  may  be 
given.  If  these  means  are  not  sufficient,  use  artificial 
respiration.  This  may  be  done  as  follows :  Place  the 


318         •  'HUMAN   PHYSIOLOGY  CHAP. 

person  on  his  back  with  something  under  the  shoulders 
to  keep  them  slightly  elevated.  See  that  his  tongue 
does  not  drop  back  into  the  pharynx.  Take  hold  of 
his  arms  near  the  elbows  and  slowly  raise  them  up,  so 
as  to  bring  them  together  over  his  head,  and  pull  firmly 
for  a  moment.  Then  lower  the  arms  slowly  until  they 
press  against  the  ribs,  pressing  in  firmly  for  a  moment, 
so  as  to  expel  some  air  from  the  lungs.  Repeat  this 
movement  about  sixteen  times  a  minute,  for  two  hours 
or  more,  or  until  natural  breathing  has  been  begun. 
Keep  the  person  warm  all  the  time,  using  hot  water 
bottles  or  warm  bricks  and  blankets.  As  soon  as  the 
person  can  breathe,  apply  ammonia  (smelling  salts)  to 
the  nose  and  give  him  a  little  hot  water  containing 
aromatic  spirits  of  ammonia. 

226.  Choking.  —  This  is  caused  by  some  object  like  a 
fish  bone,  a  toothpick,  a  marble,  a  peach  stone,  a  coin, 
etc.,  lodging  in  the  throat.  A  sharp  slap  on  the  back 
between  the  shoulders  may  be  sufficient  to  dislodge  the 
object.  If  the  patient  is  a  child,  hold  it  up  by  the  heels 
and  slap  it  on  the  back.  Sometimes  the  foreign  body 
can  be  seen  in  the  throat  if  the  tongue  is  pressed  down, 
and  can  be  easily  removed  with  the  forefinger.  Do  not 
be  afraid  to  reach  well  down  the  throat,  for  if  the  object 
cannot  be  removed  in  this  way  you  may  induce  the  per- 
son to  vomit  and  thus  dislodge  it.  Or  you  may  have 
the  person  drink  water,  swallow  jelly,  scraped  apple, 
mashed  potatoes,  or  any  such  soft  substance,  so  that  the 
object  may  be  forced  down  into  the  stomach.  The 
object  should  be  dislodged  as  soon  as  possible. 


xxi        FIRST  AID   IN   ACCIDENTS   AND    EMERGENCIES       319 

227.  Apparent  Drowning.  —  After  the  person  has  been 
removed  from  the  water,  place  him  on  a  flat  surface, 
face  down,  and  raise  the  hips  just  a  little  so  that  the 
water  may  be  removed  from  the  air  passages  and  the 
lungs.     Loosen  all  clothing  about  the  neck,  chest,  and 
waist.    Then  begin  artificial  respiration  (described  under 
suffocation),  and    continue    it   for   two  hours  or  more, 
unless   natural   breathing   is    restored    sooner.     At    the 
same  time  rub  the  body  vigorously  with  the  hands,  and 
keep  it  as  warm  as  possible.     When  natural  respiration 
begins,  hold  smelling  salts  to  his  nose  and  give  him  a 
little  hot  water  containing  aromatic  spirits  of  ammonia. 
Keep  the  person  quiet  and  warm  for  several  hours,  even 
after  breathing  has  been  restored.    Remember  you  must 

1 i )  remove  the  water  and  mucus  from  the  air  passages, 

(2)  restore  natural  respiration,  and  (3)  keep  him  quiet 
and  warm,  and  all  must  be  done  as  quickly  as  possible. 

228.  Fits.  —  A  fit  seldom  proves  fatal.     When  a  per- 
son has  a  fit,  see  to  it  that  he  does  not  injure  himself. 
Fold  up  a  handkerchief  and  place  it  between  the  teeth 
so  as  to  prevent  biting  the  tongue  and  lips.      Loosen 
the  clothing  about  the  neck,  chest,  and  waist,  give  plenty 
of  fresh  air,  and,  if  necessary,  sprinkle  a  little  cold  water 
in  the  face  or  on  the  chest.     Let  the  person  lie  down 
and  keep  quiet  for  several  hours,  and,  if  possible,  get 
some  sleep. 

Convulsions,  due  to  an  attack  of  indigestion,  are  not 
uncommon  among  children.  In  case  of  a  convulsion  give 
the  child  an  emetic  at  once.  Immerse  the  feet  and  legs 
or  even  the  entire  body  in  hot  water,  and  bathe  the  head 


320  HUMAN   PHYSIOLOGY  CHAP. 

and  face  in  cold  water  for  a  few  minutes.     Often  the 
cold  application  to  the  head  is  sufficient. 

229.  Bruises.  —  A  bruise  should  be  carefully  washed 
at  once,  and  then  have  cold  water  or  ice  applied  to  it. 
Be  careful,  however,  that  the  person  does  not  become 
chilled.    Keep  the  bruise  clean  and  the  injured  part  quiet 
until  the  swelling  has  gone  down  and  the  soreness  has 
disappeared.     Hot  water  may  be  used  in  place  of  cold. 

230.  Frost  Bite.  —  The  ears,  nose,  cheeks,  and  fingers 
are  the  parts  of   the  body  most  exposed   to   the  cold. 
The  skin  first  grows  bright  red  because  the  capillaries 
become  congested ;  then  it  turns  bluish  because  the  cir- 
culation  becomes    arrested ;    and,  finally,  gets   a   deep 
white  color  because  it  is  frozen.     Rub  the  frozen  parts 
vigorously  with    snow,  or  apply  ice  water    freely,  and 
remain  away  from  the  fire  until  the  circulation  has  been 
well  started.     When  the  parts  begin  to  sting  and  itch, 
bathe  them  in  cold  water  or  cold  oil.    The  person  should 
first  be  kept  in  a  cold  room,  and  the  return  to  a  higher 
temperature  should  be  as  gradual  as  possible.     If  the 
frozen  parts  are  warmed  too  rapidly,  gangrene  may  set  in. 

231.  Poisonous   Stings.  —  When   a  person    has    been 
stung  by  a  bee,  wasp,  hornet,  mosquito,  nettles,  etc.,  see 
that  the  sting  is  pulled  out  if  it  was  left  there.     Bathe 
the  wound  in  hot  water  and  squeeze  out  the  poisonous 
matter  at  once.     Then  bathe  it  with  a  strong  solution  of 
soda,  common  salt,  or  ammonia. 

232.  Poisons.  —  Send  for  the  nearest  physician  at  once. 
Unless  the  poison  is  an  acid,  give  an  emetic  to  empty 
the  stomach  as  soon  as  possible.     Stir  a  teaspoonful  of 


xxi         FIRST  AID   IN   ACCIDENTS  AND   EMERGENCIES       321 

ground  mustard  into  a  tumbler  of  warm  water,  and  give 
this  amount  every  ten  minutes  until  vomiting  is  pro- 
duced. Run  the  forefinger  down  the  throat  to  hasten 
the  act.  A  strong  solution  of  alum  or  common  salt  may 
be  used  if  mustard  is  not  at  hand.  Wash  the  stomach 
thoroughly  by  forcing  the  person  to  drink  freely  warm 
water  and  then  to  throw  it  up  ;  repeat  this  several  times. 
When  the  physician  arrives  he  will  know  what  to  do  to 
neutralize  the  poison  that  may  remain  in  the  system, 
and  to  remedy  the  injury  that  may  have  been  done. 

233.  Sprains.  —  Sprains    are    caused    by    a    sudden 
stretching  of  the  ligaments  at  a  joint.     No  bone  is  in- 
jured at  all.     Soak  some  cloths  in  cold  water  and  tie 
these  on  firmly,  so  that  the  injured  part  may  be  kept 
cool   and    have    perfect  rest.     Apply  cold  water   from 
time  to  time  and  keep  the  bandage  on  for  several  days 
if  the  sprain  is  severe. 

234.  Dislocations. — A  bone  may  be  out  of  its  proper 
position  at   a   joint,  but  still  not    injured  in   any  way. 
There  is  generally  a  deformity  noticeable  and  a  stiffness 
or  fixity  so  that  the  bone  cannot  be  moved.    Dislocations 
are  usually  very  painful,  but  not  dangerous.     The  per- 
son should  be  taken  to  a  surgeon  at  once.     Cold  water 
may  be   applied   to  relieve   pain   and   keep    down   the 
swelling  until  the  surgeon  takes  charge  of  the  case.     It 
is  a  good  thing  to  keep  the  limb  elevated  and  to  rub  it 
freely,  so  as  to  aid  the  circulation  of  the  blood  and  the 
lymph. 

235.  Broken   Bones.  —  When    a    bone    is    broken   it 
must  be  set  properly  by  a  skillful  surgeon  so  that  the 


HUMAN  PHYSIOLOGY 


CHAP. 


FIG.  163.  —  A  temporary 
sling  for  a  broken 
arm  (Zuppke). 


two  parts  may  again  grow  together  as  they  were  before. 

If  carefully  set,  there  will  be  no  deformity  whatever  in 
most  cases.  If  the  person  must  be 
carried  any  distance,  the  broken 
bone  should  be  kept  as  quiet  as  pos- 
sible. Cold  water  may  be  applied  if 
there  is  any  swelling. 

If  any  of  the  -bones  of  the  arms 
are  broken,  a  sling  may  be  made  as 
shown  in  this  figure.  In  this  way 
the  injured  part  may  be  carried  with 
little  pain.  Splints  may  be  made 
by  tying  thin  pieces  of  wood  to 
the  injured  part,  so  as  to  hold  it 
firmly  in  position  until  the  surgeon 

takes  charge  of  the  case. 

236.  Cuts  in  the  Skin.  —  All  cuts  in  the  skin  must 
first  be  carefully  washed.     Then,  if  the  bleeding  is  not 
severe,  bring  the  edges  of  the  cut  together  if  they  are  far 
apart  and  hold  them  in    position    by  placing  strips  of 
plaster  across  the  cut.     It  is  best  to  apply  some  disin- 
fecting lotion  like  carbolic  acid  (i  part  in   100),  or  some 
simple  ointment,  and  then  bandage  the  wound  as  quickly 
as  possible.     If  the  bleeding  is  severe,  measures  must  be 
taken  to  check  it  before  bandaging  the  wound.     Do  not 
change  the  dressing   of   a   cut   very  often,   but   when 
you  do,  see  that  the  wound  is  thoroughly  washed  and 
disinfected. 

237.  External  Bleeding.  —  This   may  belong  to  any 
one  of  three  different  kinds,     (i)  It  maybe    from  an 


XXI         FIRST  AID   IN   ACCIDENTS  AND   EMERGENCIES        323 

artery,  when  the  blood  is  bright  red  in  color  and  the  flow 
is  in  jets  or  spurts.  (2)  It  may  be  from  a  vein,  when  the 
blood  is  slightly  darker  in  color  and  the  flow  is  steady 
and  continuous.  (3)  It  maybe  from  ruptured  capillaries, 
when  the  blood  is  red  in  color  and  the  flow  is  very  slow, 
the  blood  simply  oozing  from  the  wound.  If  the  bleed- 
ing spot  is  not  too  large  the  most  effective  way  to  stop 
it  temporarily  is  to  press  the  thumb  and  fingers,  or  a 
piece  of  cotton  wool,  firmly  into  the  wound. 

If  the  bleeding  is  from  an  artery,  tie  a  large  hard  knot 
in  a  handkerchief,  and  place  the  knot  directly  upon  the 
artery  at  any  convenient  point  be- 
tween the  heart  and  the  bleeding 
end.  Tie  the  handkerchief  loosely 
and  twist  a  stick  as  shown  in  the 
figure  until  the  artery  is  completely 
compressed.  If  the  bleeding  is 
from  a  vein,  it  is  sufficient  to  raise 
the  part  up  and  place  a  pad  of 
cotton  wool  or  a  clean  cloth  on  the 
wound  and,  after  applying  warm 

FIG.  164.  — Checking  the 

water,  bandage  it  up  tightly.      If       flow  of  blood  from  an 
the  bleeding  is  from  capillaries,  the       artery  (ZuPPke)- 
bandage  just  mentioned  will  usually  be  sufficient  to  check 
the  flow  immediately.     If  the  loss  of  blood  is  likely  to 
prove  dangerous,  send  for  a  physician. 

238.  Nose  Bleeding.  —  Nose  bleeding  is  not  uncommon 
among  children,  and,  as  a  rule,  it  is  not  serious.  If,  how- 
ever, it  should  continue  too  long  or  occur  too  frequently, 
it  would  be  necessary  to  check  it.  A  simple  method  is 


324  HUMAN   PHYSIOLOGY  CHAP,  xxi 

the  following :  Stand  erect,  hold  the  head  up,  and  apply 
cold  water  or  ice  to  the  back  of  tJie  neck  and  to  the  nose 
and  forehead.  If  this  does  not  stop 
the  bleeding,  inject  cold  water  contain- 
ing a  little  soda  or  common  salt  into  the 
nostrils,  or  compress  the  bleeding  nostril 
completely  for  ten  minutes  by  pressing 
the  thumb  against  the  side. 

239.     Lung  and  Stomach  Bleeding.  - 
FIG.  165.  — Check-      Bleeding  from  the  lungs  is  a  very  serious 
ing  nose  bleed-      symptom.     The  blood  that  comes  from 

ing  (Zuppke).  .  : 

the  lungs  has  a  very  bright  red  color, 
and  a  frothy  appearance.  The  person  should  lie  on  his 
back  with  his  head  and  shoulders  elevated,  and  remain 
perfectly  quiet  for  several  days.  Small  pieces  of  ice 
should  be  sucked  and  swallowed  freely. 

The  blood  that  comes  from  the  stomach  has  a  dark  redy 
almost  black,  color,  and  a  sour  taste,  but  it  is  never  frothy. 
It  may  be  in  quite  large  pieces  or  lumps  and  have  par- 
ticles of  food  mixed  with  it.  These  cases  are  so  serious 
that  a  good  physician  should  be  consulted. 

240.  Sore  Throat — This  is  a  very  common  illness 
among  both  children  and  adults.  It  is  due  to  many 
different  causes.  Some  kinds  of  sore  throat  are  very 
dangerous,  and,  unless  simple  home  remedies  afford  relief 
very  soon,  it  is  always  wise  to  consult  a  physician.  Salt 
and  water,  or  a  solution  of  chlorate  of  potash,  or  of 
permanganate  of  potassium  (i  part  in  10,000),  may  be 
used  as  a  throat  wash  or  gargle. 


GLOSSARY 


Ab-do'men  (Latin  abdere,  to  conceal),  the  large  cavity  of  the  body 
just  below  the  diaphragm.  It  contains  the  stomach,  the  liver, 
the  spleen,  the  kidneys,  the  pancreas,  and  the  intestines,  as  its 
principal  organs. 

Ab-sorp'tion  (Latin  ab,  from,  and  sorbeo,  sorptus,  I  drink),  the  process 
of  taking  up  fluids  into  the  blood  vessels  or  lymphatics. 

Ad'e-noid  (Greek  aden,  gland,  and  -oid,  like),  an  abnormal  growth  of 
connective  tissue  in  the  upper  part  of  the  pharynx,  often  found 
in  children. 

Ad'i-pose  (Latin  adeps,  fat),  the  form  of  animal  tissue  that  contains 
fat. 

Ad-re'nal  (Latin  ad,  to,  and  renes,  kidneys),  a  small  gland  at  the 
upper  end  of  each  kidney. 

Af'fer-ent  (Latin  ad,  to,  and  ferens,  bringing),  conducting  to  an 
organ,  as  an  afferent  nerve  or  blood  vessel. 

Al-bu'min  (Latin  albus,  white),  a  kind  of  proteid  found  in  some 
foods,  as  eggs.  It  occurs  in  plant  and  animal  tissues. 

Al-i-men'ta-ry  (Latin  alimentarius,  from  alere,  to  nourish),  a  long 
tube  that  extends  from  the  mouth  to  the  end  of  the  large  in- 
testine, in  which  the  digestion  of  food  takes  place. 

A-mce'ba  (Greek  amoibe,  change),  one  of  the  lowest  forms  of  animal 
life,  found  in  fresh  water.  It  consists  of  a  single  cell  and 
has  the  power  to  change  its  form  and  shape  as  it  moves  about. 

A-nae'mi-a  (Greek  anaimia,  want  of  blood),  a  condition  in  which  the 
blood  is  deficient  in  the  quantity  or  the  quality  of  the  red 
corpuscles. 

A-nat'o-my  (Greek  anatome,  dissection),  the  science  of  structure. 

An'ti-tox'in  (Greek  anti,  against,  and  toxicon,  poison),  a  substance 
capable  of  producing  immunity  from  certain  diseases  or  of 
counteracting  the  poisonous  effect  of  disease  germs. 

325 


326  GLOSSARY 

A-or'ta  (Greek  aorte,  the  great  artery),  the  great  vessel  which  con- 
ducts blood  from  the  left  ventricle  of  the  heart. 

Ap-pend'i-ci'tis  (Latin  appendere,  to  hang),  a  disease  of  the  vermi- 
form appendix. 

A'que-ous  hu'mor  (Latin  aqua,  water,  and  humor,  moisture),  the 
liquid  between  the  crystalline  lens  and  the  cornea  of  the  eye. 

Ar'gon  (Greek,  inactive),  an  element  contained  in  the  atmosphere 
and  remarkable  for  its  chemical  inertness. 

Ar'ter-y  (Latin  arteria,  windpipe),  a  vessel  which  carries  blood 
away  from  the  heart.  The  ancient  anatomists  supposed  the 
arteries  to  contain  air,  hence  the  name. 

Au'ri-cle  (Latin  auricula,  diminutive  of  auris,  ear),  the  upper  one 
of  the  two  chambers  of  the  heart,  so  called  from  its  resem- 
blance to  the  ear. 

Ba-cil'lus,  pi.  bacilli  (Latin  bacillum,  diminutive  of  baculum,  stick), 
a  microscopic  rod-shaped  bacterium. 

Bac-te'ri-um,  pi.  bacteria  (Greek  bakterion,  staffer  rod),  a  microscopic 
vegetable  organism  found  in  decaying  organic  matter. 

Bi'ceps  (Latin  bis*  two,  and  caput,  head),  a  muscle  of  the  upper  arm 
which  serves  to  bend  the  arm  at  the  elbow. 

Bi-cus'pids  (Latin  bis,  two,  and  cuspis,  point),  the  double  pointed 
teeth  between  the  canines  and  the  molars. 

Bile  (Latin  bilis),  a  fluid  secreted  by  the  liver  and  poured  into  the 
intestines. 

Bron'chi  (Greek  bronchos,,  windpipe),  the  t\vo  large  branches  of  the 
trachea. 

Bron-chi'tis  (Greek  bronchos,  windpipe),  an  inflammation  of  the 
mucous  lining  of  the  bronchial  tubes. 

Ca-nine'  (Latin  canis,  dog),  the  sharp,  pointed  teeth  between  the 
incisors  and  the  bicuspids  ;  so  named  because  they  are  promi- 
nent in  the  dog. 

Cap'il-la-ry  (Latin  capillus,  hair),  the  small,  hairlike  blood  vessels 
that  connect  the  arteries  and  veins. 

Car'di-ac  (Greek  kardia,  heart),  pertaining  to  the  heart. 

Car'pal  (Latin  carpus,  wrist),  pe/taining  to  the  wrist. 

Car'ti-lage  (Latin  cartilago,  bristle),  a  smooth,  solid,  elastic  con- 
nective tissue  found  between  bones,  and  forming  certain 
organs,  as  the  trachea,  larynx,  etc. 

Ca-tarrh',  an  inflammation  of  the  mucous  membrane  of  the  nose. 


GLOSSARY  327 

Cell  (Latin  cella,  hiding  place),  a  tiny  bit  of  protoplasm  containing 

a  nucleus.     The  cell  is  the  unit  of  structure. 
Cer'e-bel'lum  (Latin,  little  brain),  the  little  brain  situated  at  the  back 

of  and  below  the  cerebrum. 
Cer'e-brum.  (Latin,  brain),  the  front  brain,  occupying  most  of  the 

skull. 

Ce-ru'men  (Latin  cera,  wax),  the  wax  secreted  by  the  ear. 
Chlo'ral,  a  powerful  drug  used  to  produce  sleep. 
Cho'roid  (Greek  chorion,  skin,  and  -oid,  like),  the  second  or  middle 

coat  of  the  eyeball. 
Chyle  (Greek  chylos,  juice),  the  nutritious  portion  of  the  food  that 

has  been  digested  and  is  ready  to  be  absorbed. 
Cil'i-a  (pi.  of  Latin  cilium},  little,  hairlike  projections  found  on  the 

cells  of  the  mucous  membrane  in  some  of  the  organs,  as  the 

nose  and  trachea. 

Clav'i-cle  (Latin  clavicula,  a  little  key  or  lock),  the  collar  bone. 
Coc'cus  (Greek  kokkos,  grain,  seed),  a  form  of  bacteria,  spherelike  in 

shape. 
Coc'cyx  (Greek,  cuckoo),  the  last  four  vertebrae  of  the  spinal  column, 

consolidated  into  a  single  bone ;  so  named  from  its  fancied 

resemblance  to  the  bill  of  the  cuckoo. 

Coch'le-a  (Latin,  snail  shell),  the  coiled  portion  of  the  inner  ear. 
Con-ges'tion  (Latin  con-,  together,  and  gerere,  gestus,  to  bring),  an 

unhealthy  accumulation  of  blood  in  any  part  of  the  body. 
Con-sump'tion  (Latin  con-,  with,  and  sumere,  sumptus,  to  consume), 

a  disease  of  the  lungs. 
Con-va-les'cence  (Latin  con-,  with,  and  valescere,  to  get  strength), 

the  renewal  of  health  and  strength  after  a  disease. 
Cor'pus-cle  (Latin  corpusculum,  a  small  body),  a  small  particle,  as  a 

blood  disk. 

Cra'ni-al  (Latin  cranium,  skull),  pertaining  to  the  skull. 
Cra'ni-um,  skull. 
Deg-lu-ti'tion  (Latin  de,  down,  and  glutire,  glutitus,  to  swallow),  the 

act  of  swallowing. 
Den'drites  (Greek  dendron,  tree),  the  branches  of  a  nerve  cell  that 

carry  impressions  to  the  cell  body  of  which  they  are  a  part. 
Den'tine  (Latin  dens,  dentis,  tooth),  the  substance  composing  the 

greater  part  of  teeth . 
Der'mis  (Greek  derma,  skin),  the  under  layer  of  the  skin. 


328  GLOSSARY 

Di'a-phragm  (Greek  diaphragma,  partition),  a  large,  circular  muscle 
separating  the  chest  from  the  abdomen. 

Dif-fu'sion  (Latin  dis,  in  different  directions,  and///;/ dere,  to  spread), 
a  spreading  or  flowing  of  a  liquid  or  gas  in  all  directions. 

Di-ges'tion  (Latin  di-,  in  all  directions,  and  get'o,  gestu s,  I  bear),  the 
conversion  of  food  into  a  state  suitable  for  absorption  into 
the  blood. 

Diph-the'ri-a  (Greek  diphthera,  membrane),  a  dangerous  disease  of 
the  throat,  and  sometimes  extending  into  the  oesophagus,  the 
larynx,  and  trachea. 

Dis-in-fect'ants,  agencies  used  to  destroy  germs  of  diseases. 

Dor'sal  (Latin  dor  sum,  back),  pertaining  to  the  back. 

Ef  fer-ent  (Latin  e,  out,  andferetis,  bringing),  conveying  outward  or 
away  from  an  organ. 

Ef-flu'vi-a  (Latin  e,  out,  andflttere,  to  flow),  subtile  or  invisible  par- 
ticles given  off  by  all  substances  that  have  an  odor. 

E-lim'i-na'tion  (Latin  eliininare,  eHtninatus,  to  put  forth  from  the 
threshold),  the  process  of  discharging  waste  products  or 
foreign  substances  through  the  various  organs  of  excretion. 

E-mul'si-fy  (Latin  e,  out,  and  mulgere,  mulsus,  to  milk),  to  reduce 
from  an  oily  to  a  milky  substance  in  which  the  fat  particles 
are  in  a  very  finely  divided  state,  giving  it  the  appearance  of 
solution. 

En-am'el,  the  very  hard  tissue  covering  the  crown  of  the  teeth. 

En' do-lymph  (Greek  endo,  within,  and  lympha,  water),  the  watery 
fluid  contained  in  the  membranous  labyrinth  of  the  internal 
ear. 

En-dos'te-um  (Greek  endo,  within,  and  osteon,  bone),  the  membrane 
lining  the  hollow  cavity  of  a  bone. 

Ep'i-der'mis  (Greek  ept,  upon,  and  derma,  skin),  the  outer  layer  of 
the  skin,  commonly  called  the  scarf-skin. 

Ep'i-glot'tis  (Greek  epi,  upon,  andgfotta,  tongue),  the  cartilage  cov- 
ering the  opening  into  the  larynx  during  the  act  of  swallowing. 

Ep'i-the'li-al  (Greek  epi,  upon,  and  thele,  wart  or  nipple),  the  outer 
layer  of  cells  in  the  skin  and  mucous  membranes. 

Eth'moid  (Greek  ethmos,  sieve,  and  -oid,  like),  a  sievelike  bone  form- 
ing the  roof  of  the  nose. 

Eu-sta'chi-an  tube  (named  from  Eustachio,  a  noted  Italian  physician), 
a  small  tube  leading  from  the  pharynx  to  the  middle  ear. 


GLOSSARY  329 

Fer'ment  (Latin  fermentum,  yeast),  a  substance  causing  fermenta- 
tion, as  yeast. 
Fi'ber  (Latin  fibra,  a  fiber),  a  fine,  slender,  threadlike  substance  in 

the  tissues  of  the  body. 
Flex' or  (Ln&n  fleeter e,  flexus,  to  bend),  a  muscle  that  bends  the  part 

of  the  body  to  which  it  belongs. 
Fol'li-cle  (Latin  follis,  a  bag),  a  glandlike  tube  or  a  little  cavity,  as 

a  hair  follicle. 
Fu-mi-ga'tion  (Latin  fumigarc,fumigatus,  to  smoke),  the  cleansing 

of  infected  rooms  or  clothing  by  burning  certain  substances, 

as  formaldehyde. 
Fun'dus  (Latin,  bottom),  the  bottom  of  a  hollow  organ,  as  the  fundus 

of  the  stomach. 
Gan'gli-on,  pi.  ganglia  (Greek,  tumor  or  knot),  a  collection  or  knot 

of  nerve  cell  bodies. 

Gas'tric  (Greek  gaster,  stomach),  belonging  to  the  stomach. 
Germ  (Latin  gennen,  sprout,  bud),  a  name  applied  to  organisms 

which  give  rise  to  certain  diseases. 
Germ'i-cide  (Latin  germen,  germ,  and  cczdere,  to  slay),  a  substance 

that  has  power  to  destroy  disease  germs. 
Gland    (Latin  glanSj  acorn),  an   organ   that   manufactures   a  fluid 

that  may  be  used  in  the  body  or  that  may  be  eliminated 

from  it. 

Glottis  (Greek,  windpipe),  the  opening  at  the  top  of  the  windpipe. 
Goi'tre  (Latin  guttnr,  the  throat),  a  swelling  of  the  glands  of  the 

neck.     It  is  most  common  in  mountainous  regions,  especially 

in  Switzerland. 

Gul'let  (Latin  gula*  throat),  the  throat  or  oesophagus. 
Hab'it  (Latin  habere,  habitus,  to  keep),  a  fixed  mode  of  action. 
He-pat'ic  (Greek  hepar,  liver),  pertaining  to  the  liver. 
Hu'me-rus  (Latin),  the  large  bone  between  the  shoulder  and  elbow. 
Hy'gi-ene  (Greek  Hygeia.  the  goddess  of  health),  that  branch  of 

physiology  which  treats  of  the  laws  of  health. 
In-ci'sor  (Latin  incidere,  incisus,  to  cut  into),  a  fore  tooth  which  is 

used  in  cutting  or  biting  food. 
In-oc-u-la'tion  (Latin  inoculare,  inoculatus,  to  bud),  the  practice  of 

communicating  a  disease  to  a  person  by  putting  contagious 

matter  into  his  blood. 
In-som'ni-a  (Latin  /;/-,  not,  and  soinnus,  sleep),  sleeplessness. 


330  GLOSSARY 

In'ter-cost'al  (Latin  inter,  between,  and  costa,  rib),  between  the  ribs. 
In-tes'tine  (Latin  intus,  within),  the  lower  portion  of  the  alimentary 

canal ;  the  bowels. 
I'ris  (Latin,  the  goddess  of  the  rainbow),  the  colored  curtain  of  the 

eye  with  the  pupil  at  its  center. 
Jaun'dice  (Old  Fvenclijaumsse,  yellow),  a  disease  in  which  the  skin, 

eyes,  and  the  secretions  have  a  yellowish  color  due  to  an 

excess  of  bile  pigments  in  the  blood. 
Kre'a-tin  (Greek  kreas,  flesh),  a  product  derived  from  the  oxidation 

ofproteids. 
Lach'ry-mal   glands   (Latin   lacrima,  tear),  the  small  organs  that 

produce  the  tears. 
Lac'te-als  (Latin  lac,  lactis,  milk),  vessels  of  the  small  intestine  that 

absorb  chyle  and  carry  it  to  the  thoracic  duct ;   so  named 

from  their  milklike  color. 

Lar'ynx,  the  voice  box,  at  the  upper  end  of  the  windpipe. 
Le-gu' mi-nous  (Latin  legumen,  pulse),  a  large  family  of  plants,  in- 
cluding the  pea,  bean,  clover,  lupine,  lentil,  etc. 
Lens  (Latin,  lentil),  so  named  from  the  resemblance  of  a  double 

convex  lens  to  the  seed  of  a  lentil),  the  important  refracting 

medium  of  the  eye. 
Lig'a-ment  (Latin  ligare,  to  bind),  a  band  of  connective  tissue  that 

holds  bones  in  place,  as  at  a  joint. 
Lum'bar  (Latin  lumbus,  loin),  pertaining  to  that  part  of  the  body 

between  the  hips  and  the  floating  ribs  ;  the  loins. 
Lymph  (Latin  lympha,  water),  a  fluid  derived  from  the  blood;   it 

surrounds  all  living  cells  of  the  body. 
Lym-phat'ics,  the  small  vessels  that  carry  lymph  from  the  tissues  to 

the  blood  vessels. 

Ma'lar  (Latin  mala,  cheek),  the  cheek  bone. 

Mal'le-us  (Latin,  hammer),  a  small  bone  of  the  middle  ear,  resem- 
bling a  hammer  in  shape. 

Mas'ti-ca'tion  (Latin  masticare,  masticatus,  to  chew),  chewing. 
Me-dul'la  (Latin  medius,  middle),  the  enlargement  at  the  upper  end 

of  the  spinal  cord. 
Mem'brane  (Latin  membrana,  skin,  covering),  a  thin  tissue  used  to 

protect  organs,  either  by  lining  or  by  covering  them. 
Met'a-car'pal   (Greek  met  a,  between,  and  karpos,  wrist),  the   five 

bones  in  the  palm  of  the  hand. 


GLOSSARY  331 

Met'a-tar'sal  (Greek,  meta,  between,  and  tarsos,  the  flat  of  the  foot). 

the  five  bones  of  the  instep. 

Mi'cro-scope  (Greek  mikros.  small,  and  skopeo,  I  look  at),  an  instru- 
ment for  looking  at  very  small  objects. 
Mi'tral  valves  (Latin  mitra,  head  dress,  especially  for  a  bishop),  the 

valves  between  the  left  auricle  and  ventricle ;    the  bicuspid 

valves. 
Mo'lar  (Latin  inola,  mill,  from  inolere,  to  grind  in  a  mill),  the  last 

teeth  on  each  side  of  the  jaw  ;  the  grinding  teeth. 
Mo'tor  areas  (Latin  movere,  motns,  to  move),  those  areas  of  the 

brain  that  control  the  movements  of  the  muscles. 
My'o-sin  (Greek  niys,  myos,  muscle),  a  proteid  substance  found  in 

muscle  cells ;    one  of  the  proteid  foods  obtained  from  lean 

meats. 
Nar-cot'ic  (Greek  n'arkotikos,  from  narke,  torpor,  numbness),  a  drug 

that  produces  sleep,  as  opium. 
Nic'o-tine  (from  Nicot,  a  Frenchman,  who  first  introduced  tobacco  in 

France),  the  poisonous  element  in  tobacco. 
Ni'tro-gen  (Latin  nit  nun,  niter,  and  -gen,  producing),  an  element 

forming  about  four  fifths  of  the  air  we  breathe. 
Nu'cle-us  (Latin,  small  nut,  kernel),  the  central  mass  seen  in  nearly 

all  cells. 

Nu-tri'tious  (Latin  nutrire,  nutritus,  to  feed,  nourish),  full  of  nour- 
ishment. 
Oc-cip'i-tal  (Latin  occiput,  back  of  the  head),  relating  to  the  back  of 

the  head,  as  the  occipital   bone,   the  occipital  lobe  of  the 

brain. 
(E-soph'a-gus  (Greek  oisophagos,  from  oiso,  I  shall  bear,  and  phagein. 

to  eat),  the  tube  that  carries  food  from  the  pharynx  to  the 

stomach ;  the  gullet. 

01-fac'to-ry  (Latin  olere,  to  smell,  and  facer  e,  fact  us,  to  make),  per- 
taining to  the  sense  of  smell. 
O'pi-um  (Greek  opion,  poppy  juice),  a  drug  made  from  the  juice  cf 

the  poppy. 

Op'tic  (Greek  optikos),  pertaining  to  the  sense  of  sight. 
Or' bit  (Latin  or  bis,  a  circle),  the  eye  socket. 
Or'gan  (Latin  organum,  implement),  a  collection  of  tissues  arranged 

in  some  definite  and  compact  way  to  perform  some  special 

function. 


332  GLOSSARY 

Os-mo'sis  (Greek  osmos,  a  pushing),  the  diffusion  of  fluids  through 

membranes. 
Ox'y-gen  (Greek  oxys,  sharp,  acid,  and  -gen,  producing,  as  it  was 

supposed  to  be  present  in  all  acids),  an  element  forming  about 

one  fifth  of  the  air  we  breathe. 
Pal'ate  (Latin  palatum,  roof  of  mouth),  a  bone  forming  part  of  the 

roof  of  the  mouth  and  floor  of  the  nose. 
Pan'cre-as  (Greek,  pan,  all,  andfcreas,  flesh),  an  important  digestive 

gland  located  just  back  of  and  below  the  stomach  ;  the  sweet- 
bread. 
Par'a-site   (Greek  para,  beside,  and  sitos,  food;  parasites,  eating 

beside  another  at  his  table),  an  organism  that  lives  on  or 

within  the  body  of  another. 
Pa-ri'e-tal  bones  (Latin  paries,  a  wall),  the  large  bones  at  the  top 

and  sides  of  the  skull. 
Pa-rot' id  (Greek  para,  near,  beside,  and  ous,  otos,  ear),  the  salivary 

gland  just  below  and  in  front  of  the  ear. 
Pa-tel'la  (Latin,  small  pan),  the  kneepan. 
Pel'vis  (Latin,  basin),  the  lower  part  of  the  abdomen. 
Pen'ni-form  (Latin  penna,  feather,  and  -form),  shaped  like  a  feather. 
Per'i-car'di-um  (Greek  peri,  about,  and  kardia,  heart),  a  saclike 

membrane  covering  the  heart. 
Per'i-lymph  (Greek  peri,  around,  and   Latin   lympha,  water),  the 

liquid  found  in  the  bony  labyrinth  of  the  inner  ear. 
Per'i-os'te-um  (Greek  peri,  around,  and  osteon,  bone),  the  thin  mem- 
brane covering  a  bone. 
Per'i-stal'sis  (Greek  peri,  around,  and  stellein,  to  place,  arrange), 

the  wavelike  contractions  running  along  the  alimentary  canal, 

which  push  the  contents  onward. 
Phar'ynx  (Greek,  throat),  a  funnel-shaped  organ  back  of  the  nose 

and  mouth.     It  serves  as  a  food  passage,  as  an  air  passage, 

and  as  an  organ  of  voice. 
Plas'ma  (Greek  plassein,  to  form),  the  liquid  portion  of  the  blood. 

It  carries  the  corpuscles  and  the  solid  foods. 
Pleu'ra  (Greek,  ribs),  a  saclike  membrane  covering  the  lungs  and 

lining  the  thorax. 

Pneu-mo'ni-a  (Greek  pneumon,  lung),  a  disease  of  the  lungs. 
Pons  (Latin,  bridge),  a  band  of  nerve  tissue  connecting  the  bulb 

with  the  cerebrum  and  with  the  cerebellum. 


GLOSSARY  333 

Pro'te-ids  (Greek  protos,  first),  the  food  stuffs  that  build  tissues. 
Pro'to-plasm  (Greek  protos,  first,  and  plasma,  form),  the  original 

cell  substance,  "  the  physical  basis  of  life." 
Py-lor'us   (Greek  pyloros,  gate  keeper),  the  opening  between  the 

stomach  and  the  small  intestine ;  also  the  muscle  that  closes 

the  opening. 

Ra'di-us  (Latin,  staff,  rod,  spoke  of  a  wheel),  the  bone  of  the  fore- 
arm on  the  thumb  side. 
Res'pi-ra'tion  (Latin  re-,  again,  back,  and  spirare,  spiratus,  to  blow), 

the  process  of  taking  oxygen   into  the   blood  and  getting 

carbon  dioxid  out. 
Ret'i-na  (Latin  rete,  net),  the  innermost  coat  of  the  eyeball,  in  which 

the  fibers  of  the  optic  nerve  end. 
Sa'crum  (Latin  sacrum,  sacred  ;  os  sacrum,  the  sacred  bone,  so  called 

from  its  having  been  offered  formerly  in  sacrifices),  the  bone 

at  the  lower  end  of  the  spine  just  above  the  coccyx. 
Sa-li'va   (Latin,   spittle),  the   secretion   of  the   salivary   gland ;    it 

serves  to  moisten  the  mouth,  to  aid  in  swallowing,  and  to  aid 

in  digestion. 
Sca-lene'  (Greek  skate  nos,  uneven),  muscles  of  the  neck  that  aid  in 

breathing. 

Scap'u-la  (Latin),  the  shoulder  blade. 
Scle-rot'ic  (Greek  skleros,  hard),  the  hard,  tough,  outer  coat  of  the 

eyeball. 
Se-ba'ceouS   glands    (Latin  sebum,   grease),  the  oil  glands  of  the 

skin. 
Se-cre'tion  (Latin  se-,  apart,  and  center e,  cretum,  to  sift),  the  process 

of  forming  certain  liquids  by  the  glands  of  the  body,  as  bile, 

saliva,  gastric  juice. 

Sem'i-lu'nar  (Latin  semi-,  half,  and  luna,  moon),  shaped  like  a  half- 
moon. 
Sen'so-ry  areas  (Latin  sensus,  feeling),  the  poitions  of  the  brain  to 

which  the  incoming  stimuli  are  carried. 
Se'rum  (Latin,  whey),  the  yellowish,  watery  fluid  that  is  squeezed 

out  when  blood  clots.     . 
Sphe'noid  (Greek  sphen,  wedge,  and  -oid,  like),  a  large  bone  on  the 

under  surface  of  the  skull. 
Sphinc'ter  (Greek  sphinkter,  anything  that  binds  tight),  a  muscle 

that  surrounds  an  opening  or  tube,  as  the  pylpric  muscle, 


334  GLOSSARY 

Spi-ril'lum  (Latin  spira,  coil),  a   spiral   or  corkscrew-shaped  bac- 
terium. 
Spi-rom'e-ter  (Latin  spirare,  to  breathe,  and  -meter),  an  instrument 

used  to  measure  the  capacity  of  the  lungs. 
Sta'pes  (Latin,  stirrup),  the  third  bone  of  the  ear,  shaped  like  a 

stirrup. 
Ster'num  (Greek  sternon,  breast),  the  breast  bone.     The  ribs  are 

attached  to  it  in  front. 
Stim'u-lus  (Latin,  a  goad),  any  substance  that  can  excite  a  nerve  or 

a  muscle  to  greater  action. 
Sub-lin'gual   glands   (Latin  sub,  under,  and   lingua,   tongue),   the 

salivary  glands  under  the  tongue. 
Sub-max'il-la-ry  glands  (Latin  sub,  under,  and  maxilla,  jawbone), 

the  salivary  glands  under  the  lower  jaw. 
Su'ture  (Latin  suere,  sutus,  to  sew),  the  way  the  bones  of  the  skull 

are  joined  together;  a  kind  of  joint. 

Syn-o'vi-al  (Greek  syn,  with,  and  Latin  oinun,  egg),  a  fluid  resem- 
bling the  white  of  egg,  secreted  by  the  membrane  in  movable 

joints. 
Ten'don  (Latin  tendere,  to  stretch),  the  fibrous  tissue  at  the  ends  of 

muscles ;  a  sinew. 
Tho-rac'ic  duct  (Latin  thorax,  thoracis,  breast),  the  large  lymphatic 

trunk  that  passes  through  the  thorax  and  empties  into  the  left 

subclavian  vein. 
Tib'i-a  (Latin),  the  shin  bone. 
Tis'sue  (French  tissu,  from  Latin  texere,  to  weave),  a  collection  of 

like  cells  for  a  common  purpose. 
Tra'che-a  (Greek  trachys,  rough),  the  windpipe. 
Tri'ceps  (Latin  tres,  tria,  three,  and  caput,  head),  one  of  the  muscles 

of  the  upper  arm.     It  straightens  the  arm  at  the  elbow. 
Tri-chi'na,  pi.  trichinae  (Greek  trichinos,  hairy),  a  parasite  sometimes 

found  in  pork.    It  is  the  cause  of  the  disease  called  trichinosis. 
Tri-cus'pid  (Latin  tres,  tria,  three,  and  cnspis,  point),  the  valve 

between  the  right  auricle  and  ventricle  of  the  heart. 
Tur'bi-nate  bones  (Latin  turbinatus,  from  turbo,  a  whirl),  two  small 

bones  in  the  nasal  cavities. 
Ty'phoid  (Greek  typhos,  stupor  arising  from  fever),  a  disease  of  the 

small  intestine. 
Ul'na  (Latin,  elbow),  one  of  the  bones  of  the  forearm. 


GLOSSARY  335 

Vac'ci-na'tion  (Latin  vaccinus,  from   vacca,  cow),  the   process  of 

introducing  vaccine  (cow-pox)  through  the  skin. 
Ven'ti-la'tion  (Latin  ventilare,  ventilatus,  to  fan,  from  ventus,  venti, 

wind),  the  process  of  exchanging  foul  air  in  a  room  for  pure, 

wholesome  air. 
Ven'tri-cles  (Latin  ventriculus,  diminutive  of  venter,  stomach),  the 

thick-walled  chambers  of  the  heart. 
Ver'te-bra  (Latin,  from  verier  e,  to  turn),  the  name  of  each  of  the 

twenty-four  bones  of  the  spinal  column. 
Vil'lus,  pi.  villi  (Latin,  shaggy  hair),  the  name  of  the  tiny  projections 

of  the  mucous  membrane  in  the  small  intestine. 
Vis'ce-ra  (Latin),  the  organs  of  the  abdomen. 

Vit're-ous  humor  (Latin  vitreus,  glassy),  the  liquid  filling  the  eye- 
ball back  of  the  lens. 
Vo'cal  cords  (Latin  vox,  vocis,  voice),  the  bands  of  tissue  in  the 

larynx  that  produce  sounds  as  the  air  is  expelled  from  the 

lungs. 
Vo'mer  (Latin,  plowshare),  a  small  bone  forming  the  lower  part  of 

the  partition  between  the  nostrils. 


INDEX 


ALL  REFERENCES  ARE  TO  PAGES. 


Abdomen,  45. 
Absorption,  97. 
from  intestines,  97. 
from  stomach,  97. 
of  fats,  98. 

Accidents,  First  aid  in,  315-324. 
Accommodation,  270-271. 
Adam's  apple,  213. 
Adenoid  growths,  61-62,  216. 
Adjustable  desk,  186. 
Adrenals,  144. 
Adulterated  foods,  106,  302. 
Air,  304-305. 

Impure,  Sources  of,  62-63. 
passages,  40-46. 

Diseases  of,  59. 
Purified,  63, 
Alcohol,  34-37. 

and  digestion,  116-117. 
Appetite  for,  37. 
as  a  food,  36. 

Effects  of,  on  the  blood,  137. 
on  the  brain,  249-250. 
on  the  kidneys,  164. 
on  the  liver,  116,  249. 
on  the  mind,  250. 
on  the  morals,  249. 
on  the  muscles,  204. 
on  the  nerves  of  chest,  69. 
on  the  skin,  164. 
on  the  stomach,  116,  248. 
Alcoholic  drinks,  35-36. 
Alcoholic  spirits,  36. 
Alimentary  canal,  73-74,  116. 
Amoeba,  4. 
Ancemia,  15. 
Anatomy,  2-3. 


Antitoxin,  292. 
Anvil,  260. 
Aorta,  124,  132. 
Appendicitis,  115-116. 
Appetite,  no-iii. 

for  alcohol,  37. 
Aqueous  humor,  270. 
Arm  bone,  170. 
Arteries,  123,  124,  132. 
Ascending  vena  cava,  102,  127,  131, 
Aspirates,  215. 
Association  areas,  232,  233. 

fibers,  234. 
Asthma,  60. 
Astigmatism,  273. 
Auditory  canal,  259. 

nerve,  262. 
Axone,  222,  224. 

Bacillus,  279. 
Backbone,  see  Vertebrae. 
Bacteria,  60-61,  108-110,  114,  279. 

Diseases  due  to,  279-297. 

of  cholera,  283,  289. 

of  consumption,  61,  283,  287. 

of  diphtheria,  283,  291. 

of  grippe,  283,  296. 

of  lockjaw,  283. 

of  pneumonia,  60,283,  288. 

of  typhoid,  114,  283,  290. 
Bathing,  156-159. 

Time  of,  158. 

Value  of,  156. 
Baths,  Kinds  of,  157-158. 
Bile,  90-91. 
Bile-duct,  90. 
Bleeding,  322-324.    '  • 


337 


338 


INDEX 


Blind  spot,  272. 
Blood,  12-14,  21. 

Changes  in,  143-145. 

Circulation  of,  131. 

clotting,  14. 

corpuscles,  12-14. 

Distribution  of,  14. 

How  air  gets  in,  52. 

How  to  keep,  pure,  15. 

Quantity  of,  14. 

Rate  of,  flow,  133-134. 

Uses  of,  12. 
Bones,  167-177. 

as  levers,  207-210. 

Broken,  321-322. 

Composition  of,  174-175. 

Structure  of,  175-177. 

Table  of,  172-174. 

Uses  of,  167. 
Brain,  219,  227-230,  239. 

and  education,  241-242. 

compared  to  central  railroad  station, 
219,  221. 

Exercise  of,  240. 

of  ape,  229. 

of  bird,  229. 

of  dog,  229. 

offish,  229. 

of  man,  229. 

of  marsupial,  229. 

of  pigeon,  229. 

of  reptile,  229. 
Breast  bone,  see  Sternum. 
Breathing  and  chest  freedom,  67-69. 

Proper,  69. 

Rate  of,  55-56. 
Blight's  disease,  164. 
Bronchi,  43,  44. 
Bronchial  tubes,  43-44. 
Bronchitis,  60. 
Bruises,  320. 
Bulb,  see  Medulla. 
Burns  and  scalds,  315-316. 

Callus,  150. 

Capillaries,  126-127,  131-132. 
Carbohydrates,  see  Foods. 
Carbon  dioxid,  34, 54,  142. 
Cardiac  orifice  of  stomach,  84. 


Carpal  bones,  171. 
Cartilage,  177-178. 
Catarrh,  60. 
Cell,  4-6,  141-142,  221. 

axone,  222. 

body,  222. 

Definition  of,  6. 

dendrites,  222. 

Figure  of,  5. 

medium,  n. 

nucleus,  221. 

Per  cent  of  water  in,  21. 
Cerebellum,  228,  231. 
Cerebrum,  228,  231-234. 
Cerumen,  259. 
Chest,  45. 

Deformed,  67. 

Freedom  of,  67-69. 

Natural,  67. 
Chicken  pox,  294. 
Choking,  318. 
Cholera,  289-290. 
Choroid  coat,  266. 
Chyle,  91. 
Chyme,  85. 
Cigarettes,  38. 
Ciliated  cells,  42. 
Circulation,  Plan  of,  125. 
Clavicle,  170. 
Cleanliness,  307-308. 
Clothing,  159-161. 
Coccus,  279. 
Coccyx,  170. 
Cochlea,  261. 
Coffee,  32-33. 
Colds,  60. 

Collar  bone,  see  Clavicle. 
Colon,  89. 

Commissural  fibers,  234. 
Complemental  air,  51. 
Concha,  259. 
Consumption,  61,  287. 
Contagious  diseases,  284. 
Convulsions,  319. 
Cooking,  107-108. 
Cornea,  266. 

Corpuscles  of  blood,  see  Blood   cor- 
puscles. 
Correct  position  at  desk,  181. 


INDEX 


339 


Coughing,  50. 
Course  of  blood,  131. 
Crystalline  lens,  270. 
Curved  spine,  184-187. 
Cuticle,  see  Epidermis. 
Cutis,  see  Dermis. 
Cuts  in  the  skin,  322. 

Defective  vision,  272-274. 
Deglutition,  see  Swallouing. 
Dendrites,  222,  224. 
Dermis,  150-151. 
Descending  vena  cava,  127,  131. 
Diabetes,  164. 
Diaphragm,  45,  49. 
Digestion,  72-95. 

Intestinal,  88-89. 

Mouth,  80. 

of  certain  foods,  87. 

Stomach,  84. 

Time  required  for,  87. 
Diphtheria,  291-292. 
Diseases,  59,  308-310. 

and  bacteria,  279-297. 

Disinfection  after,  310-311. 

Schools  and,  309. 
Disinfectants,  310-311. 
Dislocations,  321. 
Dress  and  digestion,  112-113. 
Dropsy,  129. 
Drowning,  319. 
Drumhead,  260. 
Duct,  see  names  of  ducts. 
Dysentery,  290-291. 
Dyspepsia,  114. 

Ear,  259-265. 

Care  of,  264. 
Eardrum,  259. 

Eating,  Hygiene  of,  111-112. 
Effluvia,  257. 

Emergencies,  see  Accidents. 
Emulsification,  98. 
Endolymph,  262. 
Endosteum,  176-177. 
Epidermis,  150-151. 
Epiglottis,  43,  213. 
Eustachian  tube,  260. 


Exercise,  Amount  of,  200-201. 

Brain,  240. 

Massage  as,  203-204. 

Time  for,  202. 

Value  of,  199-200. 
Exhale,  48. 
Exhaled  air,  54. 
Expiration,  49. 
Eye,  Care  of,  274-276. 

Muscles  of,  267-268. 
Eyeball,  265-267,  270. 
Eyebrows,  269. 
Eyelashes,  268. 
Eyelids,  268. 

Fainting,  316-317. 
Farsightedness,  273. 
Fatigue  of  muscles,  202-203. 

of  brain,  244-246. 
Fats,  Absorption  of,  98. 

see  also  under  Foods. 
Femur  bone,  171. 
Fermentation,  35. 
Fibrinogen,  14. 
Fibula,  172. 
Fits,  319-320. 
Food,  amount  of,  27-28. 
Food  and  air,  239-240. 
Food  stuffs,  18. 
Foods,  17,  102,  301-302. 

Adulterated,  106,  302. 

Animal,  23-24. 

Carbohydrates,  18,  19-20. 

Cereals,  24. 

Definition  of,  17. 

Fats,  18,  20. 

Kinds  of.  17. 

Oxygen,  18,  22. 

Proteids,  5,  18-19. 

Pure,  105. 

Salt,  18,  21. 

Substances  taken  with,  22-23. 

Value  of  cooking,  26-27. 

Vegetable,  24-26. 

Water,  18,  20-21. 
Foot,  172. 

j)f  a.  Chinese  woman,  183. 
Foreign  body  in  eye,  275. 
Formaldehyde,  311. 


34° 


INDEX 


Freckles,  151. 
Frog's  brain,  229. 
Frog's  nerve,  224. 

Gall-bladder,  91. 

Ganglia,  235. 

Garbage,  305-307. 

Gastric  glands,  see  Glands,  Gastric. 

juice,  85. 

General  senses,  254. 
"  Gin-drinker's  "  liver,  117. 
Glands,  74-75. 

Gastric,  74-76,  86. 

Intestinal,  74-76. 

Parotid,  81. 

Salivary,  74-76. 

Sebaceous,  151. 

Structure  of,  75. 

Sublingual,  81. 

Submaxillary,  81. 

Sweat,  151. 
Glottis,  43. 
Goitre,  144. 
Grippe,  296. 


Habit,  242-244. 
Hair,  154-155. 

follicle,  154. 

Hearing,  Sense  of,  258-259. 
Heart,  45,  121-124. 

beat,  135. 

Sounds  of,  136. 
Heat,  Animal,  145. 

Loss  of,  146-147. 
Helix,  259. 
Hipbones,  170. 
"  Hob-nailed  "  liver,  117. 
Human  body,  1-2. 

compared  to  city,  6-7. 

compared  to  locomotive,  2. 

Plan  of,  72. 
Humerus  bone,  170. 
Hygiene,  Definition  of,  3-4. 

of  absorption,  105-118. 

of  digestion,  105-118. 

of  ear,  264-265. 

of  eating,  111-112. 

of  eye,  274-276. 


Hygiene  of  food,  26. 

of  nervous  system,  239-251. 

of  respiration,  59-71. 

Personal,  311-312. 

Public,  299-312. 
rlyoid  bone,  170. 

mmunity,  285. 
ncubation,  286. 
ncus,  170. 

ndigestion,  Intestinal,  114. 
Infection,  286. 
Influenza,  60,  296. 
Inhale,  48. 
Inhaled  air,  54. 
[nsane, 236. 
[nsomnia,  248. 
Inspiration,  49. 

Intestinal  digestion,  see  Digestion,  In- 
testinal. 

Intestinal  glands,  see  Glands,  Intesti- 
nal. 

juices,  89. 
Intestines,  88-90. 
Large,  103,  117. 
Iris,  266. 

Joints,  178-180. 

Classes  of,  179. 
Juice,  Gastric,  see  Gastric  juice. 

Pancreatic,  see  Pancreatic  juice. 

Kidneys,  161-164. 

Effect  of  alcohol  on,  164. 
Kneepan,  see  Patella. 
Kreatin,  143. 

Labyrinth,  Bony,  261. 

Membranous,  261. 
Lachrymal  bone,  170. 

glands,  269. 
Lacteal,  100. 
Laryngitis,  60. 
Larynx,  42-43,  213-214. 
Leaping,  212. 
Leg,  Bones  of,  171-172. 
Ligaments,  179. 
Light,  Course  of,  271. 


INDEX 


34i 


Liver,  74,  90,  101,  116-117. 

trouble,  115. 
Lobes  of  the  Brain,  231. 

Frontal,  231. 

Occipital,  231. 

Parietal,  231. 

Temporal,  231. 
Loudness  of  tone,  214. 
Lungs,  44. 

Air  in,  47-50. 

Bleeding  of,  324. 

Capacity  of,  50-53. 

Changes  in  air  in,  54-55. 

Covering  of,  46. 

Lobes  of,  45-46. 
Lymph,  n,  14,  128,  140-141. 

nodes,  100. 
Lymphatic  duct,  128. 
Lymphatics,  128-129. 
Lymphatic  vessels,  100. 

Mad,  see  Insane. 
Malarial  fever,  295. 
Malleus,  170,  260. 
Marrow,  175. 
Massage,  203-204. 
Measles,  292-293. 
Meat,  24. 

Inspection  of,  299,  302. 
Medulla,  230-231. 
Metacarpals,  171. 
Metatarsals,  172. 
Milk,  33-34. 

Mind  and  brain,  235-237. 
Mitral  valve,  124,  131. 
Mixed  nerves,  225. 
Motor  areas,  232,  233. 

fibers,  225. 

nerves,  see  Nerves. 
Mouth,  75-76. 
Mucous  membrane,  75. 
Mumps,  294. 
Muscles,  189-218. 

Classes  of,  189. 

Food  of,  198. 

Intercostal,  47. 

Large,  195-197. 

of  expression,  212-213. 

Special  uses  of,  207. 


Muscles,  Structure  of,  192-193. 
Myosin,  193. 

Nails,  153. 
Nasal  cavities,  257. 
Nearsightedness,  272. 
Nerve,  224-225. 

cell,  changes  due  to  fatigue,  244-245, 
of  rat,  2220 

center,  226. 

fibers,  224-225. 

tissue,  221. 
Nerves,  223. 

Afferent,  223. 

Efferent,  223. 

Mixed,  225. 

Motor,  223. 

Sciatic,  223. 

Sensory,  223. 
Nervous  system,  219-237. 
Nervous  system  of  pigeon,  230. 

Sympathetic,  234. 
Nicotine,  37. 
Nose,  41-42. 

bleeding,  323. 
Nostrils,  170. 

(Esophagus,  83. 

Oil  glands,  see  Glands,  Sebaceous. 

Optic  Nerve,  267. 

Order  of  topics,  7-9. 

Organ,  Definition  of,  6. 

Organism,  Definition  of,  6. 

Organs  of  excretion,  149. 

Osmosis,  53,  97. 

Overwork,  244-246. 

Oxygen,  18,  22,  54. 

Palate  bones,  170. 

Palm  bones,  see  Metacarpals. 

Pancreas,  89-91,  144. 

Section  of,  89. 
Pancreatic  juice,  90. 
Papillae,  151,  254,  256. 
Patella,  172. 
Pelvic  girdle,  170. 
Pepsin,  85. 
Pericardium,  48,  121. 
Perilymph,  261. 
Periosteum,  176-177. 


342 


INDEX 


Peristalsis,  92-93. 

Personal  hygiene,  see   Hygiene,  Per- 
sonal. 

Perspiration,  Insensible,  152. 
Sensible,  152. 

Phalanges,  171,  172. 

Pharynx,  42-43. 

Physical  training  in  our  schools,  201- 
202. 

Physiology,  Definition  of,  3. 

Pigment,  151,  154. 

Pink  eye,  296-297. 

Pitch  of  tones,  214. 

Plasma,  Definition  of,  13. 

Pleura,  46. 

Pneumonia,  60,  288-289. 

Poisonous  stings,  320. 

Poisons,  320-321. 

Polypi,  216. 

Pons,  228,  231. 

Portal  vein,  100-101. 

Posture,  180-187. 

Projection  fibers,  233. 

Proteids,  see  Foods. 

Protoplasm,  4. 

Public  health  and  personal  hygiene, 
299-314. 

Pulmonary  arteries,  123. 

Pulse,  136-137. 

Pupil,  266. 

Pyloric  orifice,  84. 

Pylorus,  84. 

Radius,  170. 
Reflex  acts,  226. 
Reserve  air,  51. 
Residual  air,  52. 
Respiration,  40-58. 

Artificial,  317. 

Hygiene  of,  59-72. 
Rest,  202-203. 

and  sleep,  246-248. 
Retina,  267. 
Ribs,  48,  170. 

Round  shoulders,  184-187. 
Running,  211-212. 

Sacrum,  170. 
Saliva,  81. 


Salivary  glands,  see  Glands. 
Salts,  see  Foods. 
Scalene  muscles,  47. 
Scapula,  170. 
Scarfskin,  see  Epidermis. 
Scarlet  fever,  292. 
Sclerotic  coat,  266. 

Sebaceous  glands,  see  Glands,  Seba- 
ceous. 

Semilunar  valve,  124. 
Sensations,  253-254. 
Sensory  areas,  232. 

fibers,  225. 

Sensory  nerves,  see  Nerves. 
Serum,  14. 
Shoes,  159-160. 
Shoulder  blade,  see  Scapula. 
Sight,  Sense  of,  265. 
Singing,  216. 
Sitting,  211. 
Skeleton,  167. 
Skin,  150-166. 

Appendages  of,  153. 

Care  of,  155-156. 

Glands  of,  1^1-153. 
Skull,  168. 

of  Flathead  Indian,  183. 
Sleep,  246-248. 
Smallpox,  293-294. 
Smell,  Sense  of,  257-258. 
Solar  plexus,  235. 
Sore  throat,  324. 
Sound,  Definition  of,  258. 

wave,  263. 
Speech,  215. 
Spinal  cord,  225-227. 

ganglion,  226. 
Spirillum,  279. 
Spirometer,  50. 
Spleen,  144-145. 
Sprains,  321. 
Standing,  210-211. 
Stapes,  170,  260. 

Starches  and  sugars,  see  under  Foods. 
Sternum,  170. 
Stomach,  84-86. 

bleeding,  324. 

Sublingual  glands,  see  Glands,  Sublin- 
gual. 


INDEX 


343 


Submaxillary  glands,  see  Glands,  Sub- 
maxillary. 
Subvocals,  215. 
Suffocation,  317-318. 
Sunstroke,  316. 
Supplemental  air,  51. 
Swallowing,  82-84. 
Sweat  glands,  see  Glands. 
Swimming,  212. 
Symmetrical  posture,  182. 
Synovial  fluid,  179. 
System,  Definition  of,  6. 

Tarsal  bones,  172. 
Taste  buds,  256. 

Sense  of,  256-257. 
Tea,  32-33. 
Teeth,  76-80. 

Care  of,  108-110. 

Structure  of,  78-80. 
Temperature,  Regulation  of,  147. 
Tendon  of  Achilles,  192. 
Tendons,  192. 
Thigh  bone,  see  Femur. 
Thoracic  duct,  100,  128. 
Thought  centers,  233. 
Thyroid  bodies,  144. 

starvation,  144. 
Tibia,  172. 
Tidal  air,  51. 

Tight  clothing,  67,  112-113,  X59- 
Tissue,  Definition  of,  6. 
Tobacco,  37-38. 

Effects  of,  on  the  brain,  250-251. 
on  the  heart,  137. 
on  the  muscles,  204. 
on  the  nervous  system,  250. 
Tones,  214. 
Tongue,  256-257. 
Tonsils,  76. 

Enlarged,  216. 
Touch  bodies,  255. 

Sense  of,  254-255. 
Trachea,  43-44. 


Tree  of  life,  231. 
Trichinae,  26. 
Tricuspid  valve,  124,  131. 
True  skin,  see  Cutis. 
Turbinated  bone,  170. 
Typhoid  fever,  31,  114,  290. 

Ulna,  170. 
Urea,  162. 

Venae  cavae,  see  Ascending  vena  cava 

and  Descending  vena  cava. 
Ventilation,  64-66. 

Method  of,  66-67. 
Ventricles,  122. 
Vermiform  appendix,  115. 
Vertebrae,  170. 
Villi,  98-100. 
Vitreous  humor,  270. 
Vocal  cords,  214. 
Voice,  Care  of,  216-217. 

sounds,  214-215. 
Vomer,  170. 
Vowel  sounds,  215. 

Walking,  211-212. 
Wastes,  143. 
Water,  18,  20-21. 

contaminated  by  surface  drainage,  31. 

Filtered,  32. 

Ice,  32. 

Impure,  31,  303. 

Pure,  30. 

supply,  302-304. 
Whooping  cough,  294. 
Windpipe,  see  Trachea. 
Wrist  bones,  see  Carpal  bones. 

X-ray  photograph   of  hand,    Frontis- 
piece. 

Yeast  plants,  34-35. 
Yellow  fever,  295-296. 
Yellow  spot,  272. 


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North  America  and  South  America  together  in  one  volume. 

The  following  Supplementary  Volumes  have  also  been  prepared,  and  may  be 
had  separately  or  bound  together  with  the  Third  Book  of  the  Three  Book  Series, 
or  the  Fifth  Part  of  the  Five  Book  Series : 

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PUBLISHED  BY 

THE    MACMILLAN    COMPANY 

66    FIFTH    AVENUE,    NEW    YORK 
CHICAGO  BOSTON  SAN  FRANCISCO  ATLANTA 


An  Ancient  History  for  Beginners 

By  GEORGE  WILLIS  BOTSFORD,  Ph.D. 

Lecturer  in  Ancient  History,  Columbia  University 

i2mo  Half  Leather  $1.50  net 


"The  decided  merit  of  Professor  Botsford's  books  seems  to  be  vitality, 
thorough  grasp  of  the  subject,  and  charm  of  presentation."  —  A.  F.  BARNARD, 
Chicago  Manual  Training  School,  Chicago,  111. 

"  My  class  have  found  it  first  of  all  interesting.  Besides  this,  they  have 
gained  a  real  appreciation  of  the  ancient  civilization  about  which  they  have 
studied.  The  work  is  broad  and  scholarly  in  its  treatment,  but  at  the  same 
time  written  in  such  a  clear,  simple  manner  that  the  pupils  have  studied  it  un- 
derstandingly  and  with  sympathy."  —  Miss  MABEL  CHESLEY,  High  School, 
Fulton,  N.Y. 

"  In  this  book  are  preserved  the  excellent  features  which  render  the  author's 
histories  of  Greece  and  Rome  so  superior  to  other  school  histories."  —  Miss 
M.  EDNA  WAKEFIELD,  High  School,  Haverhill,  Mass. 

"  Botsford's  Ancient  History  for  Beginners  was  put  into  our  Normal  School, 
Preparatory  Course,  as  the  basal  text-book  in  ancient  history  just  as  soon  as 
it  was  issued.  We  like  the  book."  — Miss  BLANCHE  E.  HAZARD,  Rhode 
Island  Normal  School,  Providence,  R.I. 

"  Botsford's  Ancient  History  should  have  an  extensive  use.  It  is  one  of  the 
few  books  not  too  difficult  for  secondary  schools." — PROF.  T.  F.  MORAN, 
Purdue  University,  Lafayette,  Ind. 

"  A  close  acquaintance  with  Botsford's  Ancient  History  confirms  me  in  my 
first  opinion  of  the  book  as  the  best  elementary  work  on  ancient  history  that 
has  yet  appeared.  I  have  recommended  it  for  use  in  all  Missouri  schools 
where  free  choice  of  text-books  is  allowed."  —  N.  M.  TRENHOLME,  University 
of  Missouri,  Columbia,  Mo. 

"  I  have  carefully  examined  your  Botsford's  Ancient  History  and  have  given 
it  a  thorough  test  in  class  work.  It  gives  a  clear,  forcible,  condensed  narration 
of  ancient  history  and  includes  accounts  of  many  of  the  important  discoveries 
of  recent  years  which  have  a  direct  bearing  on  Roman  and  Grecian  history. 
I  heartily  recommend  it  for  use  in  any  high  school."  —  A.  H.  WINDER,  Asst. 
Prin.  of  High  School,  Dayton,  Ohio. 

"  After  a  careful  examination  of  your  Ancient  History  I  pronounce  it  one  of 
the  finest  on  the  market.  Botsford  is  certainly  a  historian  in  every  sense.  We 
shall  put  in  the  book  as  soon  as  opportunity  offers.  This  is  the  best  indorse- 
ment I  can  give  it."  —  J.  F.  BERGEN,  Superintendent  of  Schools,  Mineral 
Point,  Wis. 

THE    MACMILLAN    COMPANY 

66  Fifth  Avenue,  New  York 

BOSTON  CHICAGO  SAN  FRANCISCO  ATLANTA 


A  HISTORY  OF  GREECE 
For  High  Schools  and  Academies 

By  GEORGE  WILLIS  BOTSFORD,  Ph.D. 

Instructor  in  the  History  of  Greece  and  Rome  in  Harvard  University 

8vo.        Half  Leather.        $1.10  net 

"  Dr.  Botsford's  '  History  of  Greece '  has  the  conspicuous  merits  which  only  a  text-book 
can  possess  which  is  written  by  a  master  of  the  original  sources.  Indeed,  the  use  of  the  text 
of  Homer,  Herodotus,  the  dramatists,  and  the  other  contemporary  writers  is  very  effective, 
and  very  suggestive  as  to  the  right  method  of  teaching  and  study.  The  style  is  delightful. 
For  simple,  unpretentious  narrative  and  elegant  English  the  book  is  a  model.  In  my  judg- 
ment, the  work  is  far  superior  to  any  other  text-book  for  high  school  or  academic  use  which 
has  yet  appeared.  Its  value  is  enriched  by  the  illustrations,  as  also  by  the  reference  lists  and 
the  suggestive  studies.  It  will  greatly  aid  in  the  new  movement  to  encourage  modern  scien- 
tific method  in  the  teaching  of  history  in  the  secondary  schools  of  the  country.  It  will  be 
adopted  by  Stanford  as  the  basis  of  entrance  requirements  in  Grecian  history." 

—  PROFESSOR  GEORGE  ELLIOT  HOWARD,  Stanford  University,  Cal 

A  HISTORY  OF  ROME 
For  High  Schools  and  Academies 

By  GEORGE  WILLIS  BOTSFORD,  Ph.D. 

Instructor  in  the  History  of  Greece  and  Rome  in  Harvard  University 

8vo.        Half  Leather.        $1.10  net 

TEACHABLE  QUALITIES 

1.  Treatment  of  the  external  and  internal  history  of  the  Republic  in  separate  chapters; 
this  conduces  to  simplicity,  continuity  of  thought,  and  hence  interest. 

2.  Each  chapter  corresponds  with  a  period  or  epoch ;  this  helps  the  pupil  to  gain  a  distinct 
conception  of  each  period,  and  to  a  correct  arrangement  and  subordination  of  events.     In 
most  books  the  chapters  are  arbitrary  divisions. 

3.  Marginal  headings  —  sufficiently  bold  to  be  used  as  topics,  but  they  do  not  interrupt 
the  thought,  or  break  the  interest,  as  they  would,  were  they  extended  across  the  page. 

4.  Frequent  quotation  of  sources;    makes  the  subject  more  vivid  and  real. 

5.  Concrete  treatment  of  the  constitution.     This  book  represents  the  people,  senators,  and 
magistrates  as  living,  thinking,  acting,  governing,  etc.     It  does  not  treat  Rome  as  an  abstract 
legal  or  political  system,  but  as  a  city  made  up  of  human  beings. 

6.  Movement  —  in  the  entire  book  there  is  no  isolated  paragraph;  the  thought  is  continu- 
ous throughout  and  the  verbs  are  in  the  active  voice. 

7.  The  outline  of  the  Republican  constitution,  p.  353  ff.,  serves  as  an  example  of  what 
should  be  done  in  the  preparation  of  lessons,  and  at  the  same  time  is  a  complete,  logical  pre- 
sentation of  the  only  really  difficult  subject  in  Roman  history. 

8.  The  "  Studies"  require  a  thorough  digestion  of  the  material,  and  one  who  works  them 
out  faithfully  will  be  able  to  pass  the  examination  for  admission  to  any  college. 


THE    MACMILLAN    COMPANY 

66   FIFTH   AVENUE,   NEW   YORK 
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